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All IT interview question categories
JavaScript interview questions
Call, apply and bind methods in JavaScript
The this keyword
Prototypes and prototypal inheritance in JavaScript
Closures
OOP in JavaScript (Object-oriented programming)
Set, Map, WeakSet and WeakMap in JavaScript
Type Coercion
Promise
Mutating and non-mutating Array methods in JavaScript
Promise.all, promise.race, promise.allsettled, promise.any
Spread and REST operators in JavaScript: differences and examples
Callback function
Pure functions and side effects in JavaScript
The try...catch statement
Temporal dead zone (TDZ)
What is the difference between async/await and chaining?
Execution context
Difference between primitives and non-primitives in JavaScript
What is the difference between null and undefined?
The typeof operator in JavaScript
Optional chaining operator
Lexical environment in JavaScript
for...in VS for...of in an array
Object.freeze(), object.seal() and object.assign() in JavaScript
Template literals
Destructuring assignment in JavaScript
The arguments object
IIFE, immediately invoked function expression
What are higher-order functions in JavaScript (hof)
What does the Proxy object do?
How can algorithm complexity be determined?
The instanceof operator
hoisting
What is a polyfill?
Scope of var, let and const
Currying
Shallow vs deep object copying
scope in JavaScript: types and working principles
Difference between in operator and hasOwnProperty() method in JavaScript
What is the call stack (call stack)?
Event propagation in JavaScript and its phases
Difference between event.preventdefault() and event.stoppropagation()
How do you implement function memoization?
Boxing and unboxing in JavaScript
NaN
The var and closures pitfall in a loop
Differences between arrow Function, Function declaration and Function expression
The queueMicrotask() function
How does event.target differ from event.currentTarget?
Event delegation (Event Delegation)
JavaScript modules: import/export
defer vs async in a script tag
What is idempotence?
Garbage collector (GC)
What WeakRef does
Immutable and mutable data
async/await for asynchronous requests
Data types in JavaScript
Loose (==) vs strict (===) equality in JavaScript
Strict mode in JavaScript
Static methods in JavaScript
setTimeout and setInterval in JavaScript
What is promise chaining in JavaScript
What is a dead letter queue?
How to copy an Object in JavaScript?
Scope in JavaScript
Why typeof null is object
Accessing a non-existent object property
Errors and error handling
spread when calling a function
Function Constructor
toString() on a function
wrapper function
Decorator function
Partial application
Currying vs partial application
Function composition
Errors inside functions
Missing property
What does Object.defineProperty() do?
What does Object.create() do?
What is a "property descriptor"?
The writable, enumerable, configurable flags?
The ... spread operator
Data types in JS
== vs ===
Ways to declare a variable: var, let, const
Ways to declare a variable
What is scope (variable visibility)?
Variable before declaration
Hoisting mechanism
Dynamic typing
The typeof operator
typeof null
Explicit and implicit type conversion
Why [] == false returns true
[] == false ??
Increment and decrement
Increment and decrement
The ! operator (logical NOT)
The ! operator
The in operator
The in operator
The delete operator
The delete operator
The instanceof operator?
The new operator
The void operator
The void operator
Ternary operator
The && operator
The && operator
The nullish coalescing operator (??)
Nullish coalescing operator
Truthy/falsy values
Nonexistent object property
String concatenation
What is JSON?
Working with JSON: stringify and parse
Working with JSON
Checking whether a value is an array
Checking for an array
By reference or by value
Pass by value vs pass by reference
Primitives and objects in memory
Immutable/mutable data
Symbol in JavaScript
Symbol in JS
BigInt vs Int
BigInt vs Number
Property presence in an object
Checking whether a property exists in an object
Creating an object
Ways to create an object
Spread operator
Errors and their handling
Optional chaining operator
Conditional constructs
Conditional statements
break in switch
Types of loops in JS
Types of loops in JS
The continue keyword
The continue keyword
The break keyword
The break keyword
The for of loop
The for in loop
The label statement in JavaScript
The label operator
The throw statement in JavaScript
Global variables
Why is eval dangerous?
Why eval is dangerous
Arrow functions vs regular functions
Function declarations
Ways to declare functions
Function declaration vs function expression
Difference between FD and FE
Anonymous functions
Arguments by value
Passing arguments by value or by reference
Closures
Function context
Function context
The arguments keyword
...rest parameters
Default parameters
When is it better not to use arrow functions?
IIFE
Function.prototype.call
Function.prototype.apply
Function.prototype.apply
call vs apply
call vs apply
Function.prototype.bind
Function.prototype.bind?
Explicitly setting this in JavaScript
Function factory
Factory function
Wrapper function
Generators
Generator functions
function* in JS
The function* keyword
The yield operator in generators
Yield in generators
What a generator call returns
Generator return value
Yield inside () => {}
Yield inside an arrow function
Generators and iterators
this in JavaScript
Losing context
Losing the this context
Benefits of closures
What closures are used for
Mistake with var in closures and loop
Scope of a function
Scope with var | let | const
The use strict directive
use strict
Global variables
Callback function
Callback hell
Callback in another function
Passing a callback to another function
Parameters in a callback
Parameters in a callback
Synchronous and asynchronous callback
Async/sync callback
setTimeout(fn, 0)
setTimeout(fn, 0)
Recursion
Base case in recursion
What problems does recursion solve
Tasks solved with recursion
Tail recursion
Replacing recursion with a loop
Deep recursion
Deep recursion
Higher-order function
Higher-order function
Pure function
Pure function
Side effects
Side effects
Stateless function
Stateless function
Immutability in functions
Immutability in functions
Currying
Implementing compose
Implementing compose
Errors inside functions
Object in JS
Ways to declare an object
Ways to declare an object
Object vs array
Key-value
Key-value pairs
New property in an object
Adding a property to an object
Deleting a property from an object
Removing a property from an object
Checking whether a property exists in an object
Checking whether a property exists in an object
The Object.keys() method
Object.keys()
The Object.values() method
The Object.entries() method
Object.entries()
Copying an object
How do you make a deep copy of an object?
Deep copy of an object
Why the = operator does not copy an object
Why can't you copy an object with the = operator?
Copying with Object.assign
Copying through Object.assign
structuredClone
structuredClone
Object literal
Bracket notation
Missing property vs undefined value
Property shorthand
Property shorthand ({ x, y })
Getters and setters in an object
Object methods after creation
Adding methods after an object is created
Readonly properties
Read-only properties
What does Object.assign() do?
Object.create()
Object.freeze() in JavaScript
What does Object.freeze() do?
Object.seal() in JavaScript
What does Object.seal() do?
What does Object.preventExtensions() do?
Object.preventExtensions() in JavaScript
What is a prototype?
Prototype chain
What is stored in __proto__
How does __proto__ differ from prototype?
Pure object without prototype
Clean object without a prototype
Property lookup in the prototype chain
Property lookup in the prototype chain
instanceof and prototypes
this inside an object method
toString() on an object
What does the toJSON() method do?
The toJSON() method in JavaScript
The writable, enumerable and configurable flags
What does Reflect.defineProperty() do?
Reflect.defineProperty()
How does Reflect differ from Object?
What is a trap (traps)?
Proxy traps
Array map method
Array filter method
Filter in an array
forEach in an array
Array find method
find() in an array
reduce() in an array
Array reduce() method
some() in an array
Array some() method
every() in an array
Array every() method
sort() in an array
Array sort() method
flatMap() vs map()
Creating an array
How to work with an array
Array index
typeof for an array
typeof []
Array check
Checking whether a value is an array
Different data types in an array
Mixed data types in one array
Changing an array length manually
Changing length manually
delete arr[0]
The delete operator on an array
delete vs splice()
Accessing a non-existent array index
Accessing a nonexistent index
"dense" and "sparse" array
Dense and sparse arrays
How to get the last element of an array?
The push() method
What does push() do?
What does pop() do?
The pop() method
What does shift() do?
The unshift() method
What does unshift() do?
push() vs concat()
What does splice() do?
The splice() method
What the reverse() method does
What does reverse() do?
Sorting an array of numbers
Sorting an array of numbers
What the join() method does
What does join() do?
What the split() method does
Shallow copy of an array
Shallow copy of an array
What does Array.from() do?
The Array.from() method
What does Array.of() do?
What is an array-like object?
What does copyWithin() do?
The copyWithin() method
What does toReversed() do?
What does toSorted() do?
The toSorted() method
The toSpliced() method
What does toSpliced() do?
for...in vs for...of on an array
Destructuring with skipped elements
What is a two-dimensional array?
Two-dimensional array
Iterating a two-dimensional array
How to iterate a two-dimensional array?
Flattening a nested array
Flat array from a multidimensional array
WeakSet in JavaScript
What is WeakSet?
What is Map?
map VS object
Map vs object
WeakMap vs Map
WeakMap VS Map
What is asynchrony in JavaScript?
Asynchrony in JavaScript
Why JavaScript is considered single threaded
Why is JS considered single-threaded?
What the term non-blocking means
Synchronous vs asynchronous code
Synchronous VS asynchronous code
Multithreading in JS?
Blocking operation
Blocking operation
What is the event loop
What is the event loop?
Task queue in JavaScript
What is the task queue?
Microtasks in JavaScript
What are microtasks (microtasks)?
Micro vs Macro tasks
Microtasks vs macrotasks
Infinite loop
Infinite loop
Types of asynchronous operations
What setTimeout() does and returns
What does setTimeout() do and return?
What does setInterval() do?
setTimeout(fn, 0)
setTimeout(fn, 0)
Timer accuracy guarantee
Timer execution guarantee
Nested timers
Nested timers
What does queueMicrotask() do?
What does requestAnimationFrame() do?
The requestAnimationFrame() function
The requestIdleCallback() function
What does requestIdleCallback() do?
What is a callback function?
Callback function
What is "callback hell"?
What is callback hell
What is a Promise?
When is a promise considered "fulfilled"?
Promise states
How does resolve differ from reject?
Difference between resolve and reject
then, catch, finally
How does promise chaining work?
Promise chaining
What does Promise.all() do?
Promise.all() in JavaScript
Promise.allSettled() in JavaScript
Promise.race() in JavaScript
What does Promise.race() do?
Promise.any() in JavaScript
What does Promise.any() do?
How to cancel a promise?
What do AbortController and AbortSignal do?
Promise.withResolvers()
What does Promise.withResolvers() do?
How does a "promise microtask" work?
The promise microtask
The async keyword
What does an async function return?
What await does
What does await do?
What happens if you don't use await?
What happens if you omit await
Why await pauses only the current function
Blocking the current function with await
await and arrow functions
await in arrow functions
Errors in async
Error handling in async functions
What does the Web API do in the browser?
What Web API does in the browser
Macrotask queue
What is the "microtask queue"?
How does WebSocket work?
Streams: ReadableStream and WritableStream
How do streams (ReadableStream, WritableStream) work?
Web Workers in JavaScript
What does a Web Worker do?
What does postMessage() do between threads?
postMessage() between threads
Why a Web Worker has no DOM access
Why doesn't a Web Worker have access to the DOM?
SharedWorker in JavaScript
What does SharedWorker do?
What does a Service Worker do?
Service Worker
What is the DOM tree?
The DOM tree
Difference between DOM and HTML
What is document?
The document object
What is window?
The window object
The difference between window and document
How does window differ from document?
What does navigator do?
The navigator object
What does the history object do?
DOM selectors in JavaScript
Selectors for working with DOM elements
How do you create an element in the DOM?
Creating a DOM element
How to remove an element from the DOM?
Security and innerHTML
Security and innerHTML
Attributes vs properties of a DOM element
What are data-* attributes?
What is an event in the DOM?
addEventListener and removeEventListener
What do addEventListener() and removeEventListener() do?
How does onclick differ from addEventListener()?
onclick vs addEventListener
The event.target property
What does event.target do?
The event.stopPropagation() method
What does event.preventDefault() do?
The event.preventDefault() method
Event bubbling
Event bubbling
Event delegation
Event capturing
What is "event delegation"?
await in an event handler
await inside an event handler
An anonymous function as a handler
Cancelling form submission
What does form.reset() do?
The form.reset() method
Blocking page scroll
How to disable page scrolling?
What does IntersectionObserver do?
IntersectionObserver
How does MutationObserver work?
MutationObserver
window.location
What does window.location do?
What does localStorage do?
localStorage
What does sessionStorage do?
sessionStorage
localStorage VS sessionStorage
How does DOMContentLoaded differ from load?
What does the beforeunload event do?
The beforeunload event
What does the unload event do?
The unload event
What does defer do in <script>?
The defer attribute in script
The async attribute in script
What does async do in <script>?
What is the Canvas API?
What is Shadow DOM?
Shadow DOM vs regular DOM
Shadow DOM vs DOM
What is indexedDB?
What is a class constructor?
What is a class in JavaScript?
Class vs constructor function
How does a class differ from a constructor function?
Is it possible not to define a constructor?
Can you omit the constructor
How do you add a method to a class?
How to add a method to a class
Class method VS function in an object property
What does this do inside a class?
How do arrow methods differ from regular ones?
Arrow methods vs regular methods
Class as an expression const A = class {}
A class as an expression const A = class {}
The extends keyword
The super keyword
What does the super() keyword do?
Multiple constructors in a class
Multiple constructors in a class
What does return do inside a constructor?
return inside a constructor
Default values for properties
What does the static keyword do?
The static keyword in classes
How to call a static method
How do you call a static method?
Private properties
Private class properties
Private class fields outside a class
Inheriting private class fields
Can private properties be inherited?
Getters and setters in a class
Getters and setters
Classes and prototypes
How are classes related to prototypes?
Checking a class instance
Checking for a class instance
What is an error in JavaScript?
What happens when an error occurs
Syntax error VS runtime error
Syntax error vs runtime error
What is an exception?
What is an exception
What the throw statement does
What does the throw operator do?
Types of errors in JavaScript
What types of errors exist in JavaScript?
How to create a custom error type
How do you create a custom error type?
What does the try...catch construct do?
When the catch block runs
When does the catch block run?
The finally block
What does the finally block do?
Does finally run if try has a return?
A new error thrown inside catch
Throwing an error manually
How do you create an error manually?
What a stack trace contains
What does the call stack (stack trace) contain?
What does instanceof Error do?
Extending Error with custom properties
How to extend Error with custom properties?
What does catch() do in promises?
Errors in async functions
Errors in async functions
What is debugging?
Browser debugging methods
Browser debugging techniques
What does the debugger statement do?
The debugger statement
ES6 and why it is the most important update
ES6 as the most important JS update
How do let and const differ from var?
The difference between let, const and var
What are arrow functions?
Destructuring
What is destructuring?
Default values in destructuring
What does the ... operator do?
Spread and rest operator
Difference between spread and rest
Template literals
Tagged template literals
What does a "tagged template literal" do?
Classes in JavaScript
Classes in JS
import/export
What is "tree shaking"?
What did ES6 bring for asynchrony?
What ES6 brought for async code
What is a promise?
The Map collection in JavaScript
What is Map?
What does Set do?
The Set collection in JavaScript
What is Symbol?
The Symbol type in JavaScript
What is an iterator?
Proxy, traps
Proxy and the get and set traps
The Reflect object
What does Reflect do?
What is BigInt?
The structuredClone() function
What does structuredClone() do?
Performance evaluation metrics
Metrics for evaluating performance
Bottlenecks in JS code
Bottlenecks in JS code
CPU-bound and I/O-bound tasks
Single-threaded JS
What does "non-blocking code" mean?
Non-blocking code
What is memoization?
Function memoization
Input size and performance
Input data size
What is a "bottleneck" in algorithms?
What is a memory leak in JS?
Memory leaks in JS
The garbage collector (GC) in JavaScript
What does the garbage collector (GC) do?
What is "tree shaking"?
Timers and event listeners
Timers and event listeners
Profiling memory usage
How to profile memory usage?
Reflow and repaint
What are "reflow" and "repaint"?
Batching DOM updates
Batching DOM changes
Why is virtual DOM used?
Array methods vs loops
Array methods vs loops
Blocking the event loop
Why not to block the event loop?
Splitting a heavy task into chunks
What does a Web Worker do?
Minimizing HTTP requests
Minimizing HTTP requests
What is "lazy loading"?
What is "code splitting"?
Tree shaking
What does "tree shaking" do?
Code minification
Code minification
How does "defer" differ from "async" in <script>?
Scripts in head
Scripts in head
Dynamic import()
How to measure JS code performance?
Measuring JS code performance
How do WeakMap and WeakSet help the garbage collector?
What does "debounce" do?
What does "throttle" do?
Throttle in JavaScript
What does Core Web Vitals measure?
Core Web Vitals
Execution context components
What is an execution context made of?
Scope chain (chain of scopes)
Lexical scope in JavaScript
Lexical scope
Global object
A loop with var and setTimeout
Loop with var and setTimeout
Event loop in detail
What does AbortController do?
AbortController in JavaScript
What is the garbage collector (Garbage Collector)? Explain in detail how it is structured
How to avoid memory leaks
How do you avoid memory leaks?
Property descriptor
What is a property descriptor?
What does Proxy do?
The Proxy object
The Reflect object
What does Reflect do?
Why is Reflect needed together with Proxy?
What is an iterator?
Iterator
What is a generator (function*)?
Generators and yield
Async generator
Tree shaking
How does "tree shaking" work?
What is "top-level await"?
Top-level await
Dynamic import
Dynamic import
Why eval() is dangerous
Why is eval() dangerous?
What does WeakRef do?
What SharedArrayBuffer does
What does SharedArrayBuffer do?
What is the Temporal API?
Temporal API in JavaScript
React interview questions
React fiber and virtual DOM update process
What does "SSR + Hydration" mean?
React.lazy And suspense — lazy components in React
What is reconciliation?
Reasons for component re-rendering in React
What is the difference between useCallback and useMemo?
What is batching?
All about useState
What does useEffect() do?
State management approaches in React
What is Concurrent Rendering?
React performance optimization techniques
Why is key needed in React?
component rendering order and hook calling in React
Refs in React (useRef, createref, forwardref)
What does the "Render Props" pattern do?
Rules for using hooks in React
component lifecycle methods in React
What does React.memo() do?
What are React Server Components (RSC)?
What is JSX?
Synthetic events in React
What is "prop drilling"?
What are custom hooks in React
What is Error Boundary?
useTransition and useDeferredValue in React
Difference between functional and Class components in React
What is the difference between useEffect and useLayoutEffect?
What is AbortController?
What is React and why is it needed?
What is Virtual DOM?
What does `useSyncExternalStore()` do?
How useMemo works and why is it needed
What is virtualization and why is it needed
What are WeakMap, WeakSet, and WeakRef?
What does `<React.Fragment>` do?
What is portal in React
What is children?
What is HOC?
Lifting state up in React
Why useImperativeHandle is needed in React
What does useCallback() do?
What does `useContext()` do?
React.StrictMode
What is debounce?
What is a pure Function?
What is memoization?
What are "controlled" and "uncontrolled" components?
What does useId() do?
What is closure in js?
What is "Fiber architecture"?
Immutability in React state
useReducer vs useState
What is Redux?
What is RTK Query?
What is React?
Why is React called a declarative library?
What is a component in React?
What is the declarative approach?
Why does JSX require a single root element?
Why className, not class?
What does key do in lists?
Duplicate keys in lists
Component re-render decision
Why is React DevTools needed?
What is a component in React?
What types of components exist?
Class vs functional component
What should a component return?
Default value for props
Can props be changed inside a component?
What happens if you change props directly?
How to pass JSX into another component?
What is component composition?
What is a "container component"?
What is a "presentational component"?
What is "state" (State)?
State VS props
Where is component state stored?
Changing state directly
Why doesn't setState update state immediately?
What does React do when state updates?
initialValue for useState
How to update state based on the previous value?
New object when updating state
Multiple setState calls
What is state immutability?
How do you update an array element in state?
Flat state (flat state)
useReducer vs useState
memo() and state
What does "state colocation" do?
How to create global state with useContext?
What is "derived state"
What does "state lifting" mean?
client-side state VS server-side state
What is a hook in React?
Why did hooks replace class components?
What do hooks do?
Rules of hooks
When does an effect without dependencies run?
Empty dependency array
cleanup in useEffect
Why is it important to specify all effect dependencies?
In-depth questions on useRef
useRef for accessing a DOM element
What does forwardRef() do?
What does useMemo() do?
When should you use useMemo()
When to use useCallback()?
Re-render when the context changes
How do you optimize working with context?
useReducer() vs useState()
useReducer() VS useState()
What does dispatch() do?
What does useLayoutEffect do?
When does React run useLayoutEffect()?
When should you use useLayoutEffect?
What does useInsertionEffect() do (React 18)?
What does useTransition() do?
What does startTransition() do?
What does useDeferredValue() do?
How do you create a custom hook?
Other hooks inside a custom hook
How do you separate business logic and UI with custom hooks?
What is Context in React?
What problems does Context solve?
How do you create a Context?
What does <Context.Provider> do?
Accessing context in a component
Multiple contexts in an application
How does Context work in Server Components?
Re-rendering child elements
Context optimization
What does the "selector pattern" do in context?
What does the "compound components" pattern do with context?
Why isn't Context always suitable for global state?
What is the "Context + Reducer" pattern?
What principles is Redux based on?
What does store do in Redux?
What is a reducer?
What is an action in Redux?
What does dispatch() do?
What does subscribe() do?
What is a pure reducer (a pure function)?
What does combineReducers() do?
Mutating state in a reducer
How do store, actions, and reducers interact?
What does the useSelector() hook do?
What does the useDispatch() hook do?
What is Redux Toolkit?
What is a Slice in RTK?
How does RTK implement immutability?
What does Immer.js do inside Redux Toolkit?
What does redux-thunk do?
How is a thunk different from a regular action?
What does abort() do in a thunk?
How does RTK Query cache data?
What is Effector?
Why is Effector called a "reactive state manager"?
How does Effector differ from Redux?
What is "event" in Effector?
What is an "effect" in Effector?
What is a "domain"?
What does sample() do in Effector?
What does forward() do?
What does guard() do?
What does merge() do?
What does split() do?
What does `createGate()` do
What is MobX?
makeObservable and makeObservable
What is observable in MobX?
What is a computed value in MobX?
What is action in MobX?
What does reaction() do?
How does MobX track dependencies?
What does the autorun() function do?
What does the when() function do?
Why is Zustand called a minimalist state manager?
What is a "store" in the context of Zustand?
Accessing state
Why are Zustand hooks called "selective"?
Subscribing to a field in Zustand
The unopinionated principle
What is middleware in Zustand?
What does the immer middleware do?
Transparent reactivity
Transparent reactivity
What is the "lifecycle" of a component in React?
Stages of the lifecycle
Class vs function component lifecycle
What happens when a component mounts?
What happens when a component updates?
What are "commit phase" and "render phase"?
How is the lifecycle related to the Virtual DOM?
What causes a re-render?
What does componentDidUpdate() do?
What does shouldComponentUpdate() do?
What does componentWillUnmount() do?
What does the cleanup function do in useEffect()?
useEffect as a replacement for lifecycle methods
How does React determine which components need to be updated?
What does Fiber Architecture do in the context of the lifecycle?
How is React.memo() similar to shouldComponentUpdate()?
How did React 18 change the lifecycle?
Why can React now interrupt rendering?
What does "transition" do in the render lifecycle?
Why is useEffect not guaranteed to run right after commit?
What does "flushSync()" do?
What is rendering in React?
Component re-render
What does Virtual DOM do?
What is the "diffing algorithm"?
Keys (key) and rendering
What does the Fiber architecture do in React?
Commit Phase vs Render Phase
commit phase VS render phase
Strict mode and double rendering
Passing callback functions
What does useCallback() do?
What does useMemo() do?
Optimizing long lists
What does "windowing" / "virtualization" do?
What is lazy loading of components?
Global state and performance
What does "state normalization" do?
What is batching in React?
What does startTransition() do?
What does React.lazy() do?
What are React Server Components (RSC)?
What does React Profiler do?
Declarativeness in React
Single source of truth
Component-based approach
What is a "pure function component"?
What is the "Container-Presentational Pattern"?
What are "Smart" and "Dumb" components?
Feature-Sliced Design
Feature-Sliced Design
The Colocation principle in component architecture
Domain-Driven Design in React
Module isolation
What is "Layered Architecture" in frontend?
What is a "Controlled Component"?
How is an "Uncontrolled Component" different?
What does a "Higher-Order Component (HOC)" do?
Component composition
What does the "Function as Child" pattern do?
What is the "Slot Pattern"?
What does the "Control Props" pattern do?
Custom hooks
SRP in React components
What does the "Micro-frontend" approach do with React?
What is routing in a React application?
Client-side vs server-side routing
What does the react-router-dom library do?
Why doesn't the page reload during routing?
What does MemoryRouter do?
What does the useNavigate() hook do?
What does useLocation() do?
What does useParams() do?
What does useSearchParams() do?
How do you get query parameters from a URL?
What are "nested routes"?
What does <Outlet> do?
Working with asynchronous operations
Requests in a component's body
useEffect and asynchronous code
Request on the first render
How to cancel a request inside useEffect()?
How to implement a loading indicator (Loader)?
Why can't you store promises in state?
Why cache request results?
Cache invalidation
What is an "optimistic update"?
What are "debounce" and "throttle" for requests?
What does React Query (TanStack Query) do?
What does SWR do?
Suspense and data fetching
What does useDeferredValue() do when working with asynchrony?
What does useTransition() do?
What is "startTransition()"?
Isolating API from UI
Client state VS server state
What does "idempotent request" mean?
Error in a component
Types of errors in a React application
Why does try...catch not catch errors inside JSX?
What types of errors does an Error Boundary catch?
async errors in useEffect
ErrorBoundary and Suspense
Form validation errors
Error logging
What is SSR?
SSR vs CSR
Advantages of SSR
Disadvantages of SSR
In what types of projects is SSR especially useful?
Why can SSR improve SEO?
SSR and Time to First Paint
What is hydration in the context of SSR?
HTML mismatch
What does the server do before sending HTML to the client?
What does middleware do in SSR?
JSON.stringify() and its danger
What is streaming SSR and how does it work?
SSR and lazy loading of components
How does SSR work with SPA routing?
What does useLayoutEffect() do during SSR?
Context and SSR
What are React Server Components (RSC)?
What's new in React 18?
Concurrent Rendering
createRoot() vs render()
What is batching (Automatic Batching)?
setState in React 18
What does Suspense do in React 18?
Suspense and Data Fetching
What are "Transition Updates"?
What does startTransition() do?
Concurrent Mode
Concurrent Mode
What does the useId() hook do?
What does the useSyncExternalStore() hook do?
What does the useInsertionEffect() hook do?
What does useDeferredValue() do
hydration in React 18
What is Fiber in the context of React 18?
What are React Server Components (RSC)?
Actions in React 19
What is useFormStatus?
What is useOptimistic
What's new about the use API (reading resources, Promise, etc.)?
Server Components in React 19
The importance of TS in modern applications
How does JSX differ from TSX?
How do you type state with useState()?
How do you type useRef()?
How do you type useMemo()?
How to type useCallback()?
How do you type event handlers?
How do you type context?
What is the React.ReactNode type for?
HTML interview questions
Html5 new features and apis
Semantic HTML
What is doctype in HTML
What is the DOM?
Difference between strong and b tags in HTML
Difference between script, async and defer
Essential meta tags in HTML
Web accessibility and ARIA attributes
What is HTML and what is it used for?
How is HTML related to CSS and JavaScript?
What does an HTML document consist of?
What does the browser do when loading an HTML file?
What does "tree of elements" mean?
What happens when the browser parses HTML?
What are the main sections of an HTML document?
What does the <body> element do?
What is a tag in HTML?
What is an attribute in HTML?
What does the term "semantics" mean in the context of HTML?
Why is semantic markup important for web development?
How does semantics affect SEO?
Why is it not recommended to use <div> and <span> for all page content?
Tell us about the main semantic tags used in development
What is the difference between <main> and <section>?
Why is it important to use <h1>-<h6> headings in order?
Why does correct semantics improve navigation for users with disabilities?
What tools help check HTML semantics?
What are data attributes in HTML
What is an HTML tag?
What parts make up an HTML tag?
What are paired and void tags?
Why are the <head> and <body> tags needed?
What are the main categories of tags in HTML5?
How do block elements differ from inline elements?
What is <div> used for? Why is <div> often called a "universal container"?
What is an attribute in HTML?
Does the order of attributes matter?
Which attributes are used most often in practice?
What is the id attribute used for?
What does the class attribute do?
What does the style attribute do?
What does the defer attribute do on <script>?
What does the async attribute do on <script>?
HTML forms and built-in validation
What is the <head> element in HTML?
What is contained inside <head>?
Why does the order of tags inside <head> matter?
What does the <title> tag do inside <head>?
What are meta tags in HTML?
What does <meta charset="UTF-8"> do?
What does <meta name="description"> do? Why does it matter for SEO?
What does <meta name="robots"> do?
What does <meta name="keywords"> do, and is it still relevant?
What does <meta name="viewport"> do, and why does it matter?
What are the meta tags og:title, og:description, og:image used for?
What does the <link> tag do? How is CSS linked?
What is a favicon?
How does the <form> element connect input fields and data submission?
What does the action attribute do on <form>?
What does the method attribute do on <form>?
What is the difference between the GET and POST methods when submitting a form?
What does the <input> element do?
What does <textarea> do and when should you use it?
How do you make an <input> for entering a password?
What does <select> do?
How do you add image upload to a form in HTML?
What does <label> do? How does <label> link to an input field?
How do you make the simplest radio button in HTML?
What does name do on a form field?
What does the <img> element do in HTML?
How does the browser load an image specified in src?
How to hide elements visually but keep them accessible to screen readers
What happens if the image is not found at the specified path?
Why is it important to specify dimensions (width, height) for images?
What does the loading="lazy" attribute do?
Why is it important to optimize images before loading?
What is progressive JPEG?
What does the srcset attribute do?
What does the <video> element do? How do you specify a video source in HTML?
What does the <audio> element do?
What does the <canvas> element do?
What does the <svg> element do?
How does SVG differ from raster images?
What is a link (hyperlink) in HTML?
How do you specify a link in the <a> tag?
What is the difference between absolute and relative links?
What is a fragment | anchor in a link?
How do you jump to an element by ID via a link in HTML?
How do you open a link in a new tab in HTML?
Which tag is used to group navigation links?
What are "breadcrumbs" (a breadcrumb trail)?
What is a "sitemap" and how does it relate to navigation?
What are the main elements that make up the structure of a table?
What does the <table> tag do?
What does the <tr> tag do?
What does the <th> tag do?
What does the colspan attribute do?
What does the rowspan attribute do?
What does the term "a11y" mean?
Why does accessibility matter in web development? Who does it affect?
Why is it important to ensure keyboard accessibility?
Why is it important to support accessibility for screen readers?
Why is it important to test color contrast?
What does "responsive accessibility" mean?
Why is it important to use correct HTML tags instead of <div> / <span>?
What is alternative text (alt text)?
What are the main types of ARIA attributes?
What does the role attribute do?
What tools help test accessibility?
CSS interview questions
What are Container Queries?
What is responsive web design
CSS selector specificity
CSS position property
CSS z-index and stacking context
CSS grid layout
CSS logical properties
CSS-in-js problems and solutions
What are vh, vw, vmin and vmax in CSS
CSS functions: calc(), clamp(), min(), max()
CSS selectors
What is cascade in CSS
CSS display property
CSS flexbox layout
flexbox vs CSS grid comparison
CSS properties for creating animations and smooth transitions
CSS preprocessors: SASS, SCSS, and LESS
Methods for style isolation in CSS
CSS units: px, rem, em
What is CSS and what is it used for?
What are property and value in CSS?
CSS variables (custom properties)
What are the ways to connect CSS to HTML?
What does the style attribute do inside an HTML tag?
Difference between CSS reset and normalize
Why are inline styles considered bad practice?
What does "cascade" mean in the behavior of CSS rules?
In what order are CSS rules applied?
What is "inheritance" in CSS? Which properties are inherited by default?
What absolute units of measurement exist in CSS?
What relative units of measurement exist in CSS?
What are CSS variables? How do you declare a variable in CSS?
What is "reset CSS"?
What does normalize.css do?
What is a CSS preprocessor?
What is a selector in CSS? What are selectors used for?
What does the term "specificity" mean in CSS?
How is specificity calculated? What does the specificity formula look like?
What is the priority of the ID selector?
How does declaration order affect the final style?
How do you set styles for all elements on a page?
How do you set styles by class?
How do you set styles by attributes?
What does the comma , do in selectors?
What is the difference between h1, h2, h3 and h1 h2 h3 in style declarations?
What is a pseudo-class? What pseudo-classes do you know?
What does :first-child do?
What is a pseudo-element? How does a pseudo-element differ from a pseudo-class?
What does ::before do?
How does !important affect specificity?
What ways of specifying color does CSS support?
How do you set the text color of an element?
What is the difference between rgb() and rgba()? What does the alpha channel do?
What does the value transparent do?
How do you specify a font for text?
What is a fallback font?
What does the @font-face rule do?
What units of measurement can be used for font size?
What does the line-height property do?
What is the Box Model in CSS? What parts make up the Box Model?
What is content-box?
What is padding-box?
What is "content area"?
How does overflow: auto affect block size?
What is padding?
What does margin do?
How margin differs from padding
Can margin be set to a negative value?
How does CSS calculate an element's final size?
How do inline elements differ from block elements?
What does the display property do?
What is "collapsing margins"?
What is element positioning in CSS?
How to change color in svg file?
How does CSS control the position of elements on a page?
What types of positioning exist in CSS?
What does position: relative do?
What does position: absolute do?
Why does an element with absolute "fall out" of the flow?
What does position: fixed do? What does a fixed element attach to?
What does position: sticky do?
How does the "sticking" mechanism work during scroll?
What does the z-index property do?
How does display affect the behavior of positioned elements?
CSS box-sizing property
What is Flexbox?
What is the advantage of Flexbox over float-based layout?
How do you activate Flexbox for a container?
CSS overflow property
CSS aspect-ratio
How do you set the direction of the main axis?
CSS Object-fit and Object-position
What does the flex-wrap property do?
How does flex-wrap affect the alignment of elements?
What does flex-flow do?
What does the justify-content property do?
What does align-items do?
How do you align an element individually?
What does flex-grow do?
What does flex-basis do?
What does the order property do?
What is CSS Grid Layout?
Block, inline and inline-block elements in HTML & CSS
How does CSS Grid differ from Flexbox?
What is "grid area"?
Difference between visibility: hidden and display: none
What does the grid-template-columns property do?
What does the grid-template-rows property do?
What does the fr unit mean?
What does repeat() do in Grid?
What does the grid-template property do?
What does grid-template-areas do?
What does the gap property do?
What is adaptive (responsive) design?
What does "elastic layout" mean?
What is "fluid design"?
What is a viewport in the context of the web?
What is the difference between absolute and relative units?
What is a media query? What are they used for?
What is a breakpoint in responsive design?
How do Flexbox and Grid layout help create responsive layouts?
What are container queries? How do they differ from media queries?
What is animation in CSS? How do you set it?
How does animation differ from a transition?
What are "states" in CSS animations?
What does the transition-timing-function property do?
What is @keyframes in animations?
What does transform: perspective() do?
What does the :has() selector do?
What does :is() do?
What does :where() do?
What does the lh unit do?
What does clamp() do?
What are Scroll-driven Animations?
What does subgrid do? How does subgrid differ from nested grid containers?
What does the @layer directive do?
How do you declare and use a variable in CSS?
What is a pseudo-class in CSS?
Why media queries are needed in CSS
Which pseudo-classes do you know?
What is a pseudo-element?
Which pseudo-elements do you know?
What does :hover do?
What does :root do?
What does ::before do?
Where do ::before and ::after sit in the flow?
How do pseudo-classes affect specificity?
What does the term "cascade" mean in CSS?
Why transform is better for animations than top, left
How does !important affect the order of origins?
What is inheritance in CSS?
CSS will-change property
Which properties are inherited by default?
What does the inherit keyword do?
What is BEM methodology (block element modifier)
TypeScript interview questions
What is type narrowing?
What does infer mean in TypeScript?
What is a "conditional type"?
What does "structural typing" mean?
What are union types?
Type assertions in TypeScript
What is a "mapped type"?
What is a "type guard"?
Differences between type and interface in TypeScript
What does the implements keyword do?
What is a "discriminated union"?
Differences between any and unknown in TypeScript
What is the never type?
Declaration merging in TypeScript
What does Partial<T> do?
The satisfies operator in TypeScript
Utility type awaited in TypeScript
What is execution context?
Why TypeScript is needed, pros and cons
Literal types in TypeScript
What is enum in TypeScript?
What is function overloading (overload)?
Tuple types in TypeScript
What does Exclude<T, U> do?
What does Extract<T, U> do?
What does NonNullable<T> do?
Access modifiers in TypeScript: public, private, protected, readonly
What are decorators in TypeScript?
Template literal types in TypeScript
What does Required<T> do?
What does Readonly<T> do?
What does Record<K, T> do?
What does ReturnType<T> do?
Const assertions (as const) in TypeScript
Abstract classes in TypeScript
Utility type pick in TypeScript
Utility type omit in TypeScript
What problem do hooks solve in React?
What is the n + 1 problem in GraphQL?
What is TypeScript?
Superset of JavaScript
What does "static typing" mean?
What does "strict typing" mean?
The benefit of static and strict typing
Why does TypeScript improve code quality?
Why does TS code need to be compiled?
What is tsconfig.json?
Why doesn't TS always require writing types explicitly?
What is "type safety"?
Runtime errors and TS
Primitive types
What is the string type?
What does the boolean type do?
What is the bigint type?
What does the symbol type do?
What does the void type mean?
What does the unknown type mean?
What does the any type do?
When to use any?
What does the type keyword do?
What does the interface keyword do in TS?
What is a type in TypeScript?
What is an interface in TypeScript?
What is the difference between types and interfaces?
Why are interfaces more often used for objects?
How do you set optional fields in an interface or type?
Immutable fields
Dynamic object keys
What is an index signature in an interface?
Multiple inheritance
How do you combine multiple types?
Type and interface inheritance
Same interface name
Structural typing in interfaces
Intersection types
Union of types
Recursive type
Typing function parameters
Return value type
Automatic return type inference
void in a function
Never in a function
How do you set a default parameter?
Typing async functions
How do you specify a function type in an interface or type?
How to create a function type using type?
How do you declare an array in TypeScript?
How does string[] differ from Array<string>?
Mixed types in an array
How do you declare a two-dimensional array of numbers?
What is a tuple in TypeScript?
What is Set in TypeScript?
What is Map in TypeScript?
What is a union type in TypeScript?
Combining more than two types
Combining primitives and objects
The in operator when checking a union
What does "discriminated union" mean?
Exhaustive check through never
What is an intersection type?
Intersection of primitives
Readonly | optional intersections
What is distributive behavior of union types?
Set theory
What are Utility Types in TypeScript?
What does Pick<T, K> do?
What does Omit<T, K> do?
What does ConstructorParameters<T> do?
What does InstanceType<T> do?
Utility types for strings
How do generics differ from any?
How do you declare a function with a generic parameter?
Type inference with generics
Type inference with generics
Multiple generics
Constraints in generics
How do you declare a generic type via type?
Default type in a generic
extends in generic parameters
The type does not satisfy the constraint
How to constrain a generic type to the keys of another type?
How do you extract a function's argument types with infer?
Conditional generics
T extends never
What does "union narrowing" mean?
What does infer mean in TypeScript?
Why is type narrowing needed?
What are Discriminated Unions?
Discriminant property
Index access types
Index Access Types
The keyof operator
JS vs TS typeof
JS vs TS classes
Typing a constructor
Can you overload a constructor?
Access modifiers
What does the public access modifier do?
What does the private access modifier do?
What does the protected access modifier do?
Typing class methods
What does the static keyword do?
How does a class implement an interface?
How does implements differ from extends in classes?
Can you make a generic class?
What is type narrowing in TypeScript?
When does type narrowing happen?
Code safety and narrowing
What is a type guard function?
What does "control flow based narrowing" mean?
Why is any dangerous in a project?
Type assertion (as)
Type assertion (as)
unknown vs any
unknown vs any
Generic without extends
Why is enum often considered an antipattern in TS?
ts-ignore
strict: false
strict: false
Typing for the sake of typing
Vue interview questions
How does reactivity work in Vue.js?
What does `ref()` do?
Vue components and their lifecycles
What is Vue.js?
Options API and composition API
Declarativeness in Vue.js
How does Vue update the DOM when data changes?
What is a component in Vue.js?
unidirectional data flow
What is the Options API?
What is the Composition API?
Data and UI Binding
What is a directive?
What is a Slot in Vue.js?
What is a "layout component"?
Routing and navigation
How does two-way binding (v-model) work?
What is reactivity in Vue.js?
How does Vue track data changes?
Computed, methods and watchers in Vue.js
Value of a property in data
Reactivity and declarativeness
What is nexttick in Vue.js?
reactivity VS data binding
What is the "reactivity tree"?
Proxy and the new reactivity system
Component re-rendering
Effects and reactivity
What does `reactive()` do in Vue 3?
What does toRefs() do?
What does watch() do?
Component in Vue.js
Emits and custom events in Vue.js
What are the advantages of the component approach?
How to efficiently pass data between components?
What are local and global components?
How to register a global component in Vue 3?
How do you register a local component?
Dynamic components in Vue.js
What is a component template?
async components and suspense in Vue.js
What can a component in Vue contain?
What is a component tree?
What are `props` in Vue?
Why must props be immutable?
What is emit?
What is a slot in Vue?
Lifecycle hooks
How do hooks differ in the Options API and Composition API?
What is an async component?
What is state in the context of Vue.js?
What are attribute bindings in Vue?
Local VS Global state
Custom directives in Vue.js
Where is state stored in the Options API?
What is data() in Options API?
What does state reactivity mean?
How does a component know that state has changed?
What are computed properties?
How does computed differ from a regular method?
What is watch?
What is provide/inject?
When is local state better than global state?
What is Pinia?
What are Vue directives?
V-model in Vue.js
How do directives differ from regular HTML attributes?
What does a modifier do in a directive?
What does an argument in a directive do?
What built-in directives exist in Vue?
What is v-bind used for?
What is v-on used for?
How does v-if work?
What is the difference between v-if and v-show?
How does v-for work?
What happens if you use v-for without a key?
What is v-model used for?
What are v-model modifiers?
What is v-once used for?
What does the v-memo directive do?
What is v-cloak used for?
What is v-pre used for?
What is the Vue component lifecycle?
What are the main stages of a component's lifecycle?
How to add fallback content for slots in Vue?
What is the `beforeCreate` hook used for?
When is mounted called?
When is destroyed called?
What lifecycle hooks are available in the Composition API?
What is <keep-alive>?
When do ref elements become available?
Can you use ref inside composition hooks?
What is two-way data binding?
How does the v-model directive work?
What does the .lazy modifier do?
What does the .trim modifier do?
What does the .number modifier do?
What is the difference between value and modelValue?
What does the `v-on` directive do?
What are event modifiers?
What are key modifiers?
What is $emit?
How to use ref for a form?
How to use reactive for a form?
defineProps, defineEmits, and defineExpose in Vue.js
What is the Composition API?
Can Composition API be used together with the Options API?
What is ref()?
What does reactive() do?
What is computed()?
What does shallowRef() do?
What is watch()?
What does the `deep` option do?
What does the immediate parameter do?
What lifecycle hooks are available?
How do you declare props in setup?
What is emit?
What are composable functions?
Why is provide/inject needed?
How do you access the DOM through ref?
What is the Options API?
Teleport in Vue.js
Can you mix the Options API and the Composition API?
Transition and transitiongroup in Vue.js
What does the methods object contain?
What are computed properties?
What is watch needed for?
How do you declare props?
What is $emit?
List all the lifecycle hooks.
How to declare local directives?
What are mixins?
What does extends do?
Vue router: routing and navigation guards
What is Vue Router?
What is the router used for in an SPA?
How do you declare a dynamic route?
What is the difference between params and query?
What is $router.push?
What is a navigation guard?
What is lazy loading of routes?
What is a state manager?
How does a component's local state differ from global state?
What is one-way data flow?
Which state managers are used in the Vue ecosystem?
What advantages does a central store give you?
What drawbacks does a centralized store have?
What is Pinia?
Why does Pinia replace Vuex in the Vue 3 ecosystem?
Why does Pinia have no mutations?
What is a slot in Vue?
How does virtual DOM work in Vue.js?
Can you use several slots in a single component?
What is a scoped slot?
What is a default slot?
What is useSlots()?
What is a wrapper component (wrapper component)?
What performance metrics do you know?
What is Virtual DOM?
How does Vue optimize the Virtual DOM?
What is the block tree (Vue 3)?
Why is a patch flag needed?
Why is Proxy faster than defineProperty?
What is memoization in the context of Vue?
Why is computed essentially a memoized getter?
How do you optimize large tables?
What is list virtualization?
When should you use throttle?
When should you use debounce?
What are lazy loading components?
What is tree shaking?
Why is testing important in large projects?
What is Vue Test Utils?
Angular interview questions
component lifecycle methods in Angular
Advanced dependency injection patterns in Angular
How does change detection work in Angular?
What is ngzone in Angular?
Signals in Angular
Testing in Angular (unit and integration tests)
What is Angular?
Difference between AngularJS and Angular
What is a SPA (Single Page Application)?
Why is Angular called a framework, not a library?
What does Angular CLI do?
What are the main parts of an Angular application?
What is NgModule?
What types of modules are there in Angular?
Why is it important to follow modularity in Angular?
What does the "feature isolation" principle mean?
What is an application's "entry point"?
What does "zone.js" do in Angular?
@input and @output decorators in Angular
How do you declare a component in Angular?
Content projection (ng-content) in Angular
What role does the @Component decorator play? What are the main fields in the @Component decorator?
What does the selector property do in the @Component decorator?
ViewChild and ContentChild in Angular
What does the template property do?
Standalone components in Angular
What is encapsulation in Angular components?
What types of ViewEncapsulation exist?
How does Emulated differ from ShadowDom?
What is change detection in Angular?
How does Angular track changes to properties in a component?
What does ChangeDetectorRef do?
What does the @Input() decorator do?
What does the @Output() decorator do?
What is EventEmitter?
How do you send an event from a child component to the parent?
What are "view" and "content" in the context of Angular components?
What does ng-container do?
What does ElementRef do?
What does ElementRef do?
How to dynamically create a component in Angular?
What hooks exist and in what order are they called?
How does a component receive dependencies through the constructor?
How does a standalone component differ from a regular one?
What is a directive in Angular?
What types of directives exist in Angular?
Pipes in Angular (built-in and custom)
What is a structural directive?
What is an attribute directive?
What does the ngIf directive do?
What does the ngSwitch directive do?
Can you create a custom directive in Angular?
How are directives related to DOM elements?
What does the @Directive() decorator do?
How do you register a directive in a module?
How do you limit the scope of a directive?
How do you make a directive shared?
What does ngClass do?
What does ngStyle do?
What does ngModel do?
What does @HostBinding() do?
What is the difference between a structural and an attribute directive?
What does the asterisk (*) before a directive do?
Which lifecycle hooks do directives support?
List all built-in structural directives
List all the built-in attribute directives
What are directives and what types exist in Angular?
What is a template in Angular?
What does template binding mean?
How to set a dynamic style in a template?
How does the safe navigation operator (?.) work in a template?
What is the ! operator (non-null assertion) used for in a template?
What is a template variable (#var)?
What is let- syntax in a template?
How does the $implicit variable work in a template context?
What does <ng-container> do?
What does <ng-template> do?
What is a template context?
What are modules in Angular and how are they used?
What is a modular structure in Angular?
What does CommonModule do?
What is the component lifecycle in Angular?
What lifecycle hooks exist in Angular?
In what order are the lifecycle hooks called?
What does ngOnChanges() do? When is it called?
What does ngOnInit() do? When is it called?
What does ngAfterContentInit() do? When is it called?
What does ngAfterContentChecked() do? When is it called?
What does ngAfterContentChecked() do? When is it called?
What does ngAfterViewInit() do? When is it called?
What does ngAfterViewChecked() do? When is it called?
What does ngOnDestroy() do? When is it called?
What happens if you don't unsubscribe from subscriptions?
How does ChangeDetectionStrategy affect the hooks?
How do you implement a custom change detection strategy?
How do hooks work for dynamically created components?
What is the lifecycle of an Angular application?
What does zone.js do when the application starts?
How does the loading of lazy-loaded modules work?
Services and dependency injection in Angular
What is a signal in Angular?
When were signals introduced in Angular?
Injector hierarchy in Angular
What is the main goal of introducing signals in Angular?
How to create a signal in Angular?
What is WritableSignal?
How to get the current value of a signal?
How does a signal notify about changes?
How does a signal store state?
What is a computed() signal?
How to make a chain of computed signals? (junior)
Can you use async operations inside computed()?
What is effect() in Angular?
When is effect called for the first time?
What does the cleanup function inside effect() do?
How does effect handle errors?
How to use a signal in a component template?
How does signal differ from observable in terms of reactivity?
How to convert an observable to a signal?
Can Zone.js be fully disabled when using signals?
How do signals simplify Change Detection?
Why are signals considered more performant than RxJS?
What is Dependency Injection (DI) in Angular? Why is the DI mechanism needed?
How does DI help with application modularity?
What does "inversion of control" (IoC) mean?
How is inversion of control related to DI?
What is a provider (Provider)?
Why is DI a key part of the Angular framework?
What is injection through the constructor (constructor injection)?
What does the useExisting key do?
What does the useValue key do?
What does the useFactory key do?
What does a multi-provider do?
What is the root injector (root injector)?
What is the module injector (module injector)?
What is the component injector (element injector)?
What is the scope of a dependency?
How does DI work in standalone components?
How to avoid circular dependencies?
What is a service in Angular? Why are services needed in Angular?
Difference between template-driven and reactive forms in Angular
What role does the @Injectable() annotation play?
What does "singleton service" mean?
What are factory services?
What is an adapter service?
What types of forms exist in Angular?
Angular router: routing, guards, and lazy loading
What is the difference between Template-driven and Reactive forms?
How does Angular bind form data to the component model?
What are form control directives (form directives)?
What does the ngForm directive do?
What does the ngModel directive do?
What does the formControl directive do?
What does the formGroup directive do?
What does the formArrayName directive do?
What is the dirty and pristine state?
What is the valid and invalid state?
What does the status property of a form do?
What does a pending form status mean?
What is a validator in Angular?
What types of validators are there?
How do you check if a control has an error?
What is routing in Angular?
What is RxJS and how is it integrated in Angular?
Common RxJS operators in Angular
Why is routing needed in SPA applications?
What is subject and what types of subjects exist in RxJS?
What does RouterModule do?
How does RouterLink differ from a regular <a href>?
What is a wildcard route (**)?
How do you navigate to a route programmatically?
How do you declare a route parameter?
How do you get query parameters?
What are nested (child) routes?
What are route guards?
What does CanActivate do?
What is lazy loading of routes?
What does UrlTree do?
What is state management (state management) in Angular?
How does local state differ from global state?
What does the term "single source of truth" mean?
Why does state matter for UI predictability?
How can you manage state using services?
How do signals affect the approach to state management?
What is shared state?
What is derived state?
Why is it important to avoid duplicating state?
How do you pass state between a parent and a child component?
How do you avoid "props drilling" when passing state?
What does BehaviorSubject do in state services?
How do signals replace the "observable store" pattern?
What does state normalization mean?
What is NgRx?
Why is NgRx considered the standard in the Angular ecosystem?
What are the main elements of NgRx's architecture?
What does Store do in NgRx?
What does Action do?
What does Selector do?
What does Effect do?
What is EntityAdapter in NgRx?
How does NgRx implement the Redux pattern?
What does immutability mean in the context of NgRx?
How do you connect NgRx Store to an application?
What is NGXS?
How does NGXS differ from NgRx?
What is Akita?
How does Akita differ from NgRx?
What are the main entities in Akita?
What is Observable?
What does from() do in RxJS?
What does of() do?
What does interval() do?
What does timer() do?
What is Subscription?
What does add() do on Subscription?
How to avoid memory leaks in subscriptions?
What does takeUntil() do?
What is an operator in RxJS?
What's the difference between "pipeable" and "creation" operators?
What does map() do?
What does filter() do?
What does tap() do?
What is BehaviorSubject?
What is ReplaySubject?
What does ConcatMap do?
What does mergeMap do?What does mergeMap do?
What does exhaustMap do?
What is Async pipe?
Why is server-side rendering needed in Angular?
What are the advantages of SSR over CSR?
How does SSR affect SEO?
How does SSR affect page load speed?
What is Angular Universal? How is Angular Universal related to SSR?
What is pre-rendering?
What does the ng add @angular/ssr command do?
What is hydration in Angular?
What phases does SSR rendering go through?
How does TransferState work in Angular Universal?
Frontend Tools interview questions
What is code splitting?
Why is Webpack called a "modular bundler"?
What is the "entry point" in Webpack?
What is output in webpack?
What changes when switching between development and production modes?
What are the key fields in a Webpack configuration?
What is minification?
What task do plugins perform in Webpack?
What main loaders are connected for a React frontend application?
Can you write your own plugins in Webpack?
How do you set up Webpack to run for development?
What is used to implement "micro frontends" in Webpack?
What is HMR?
What is HMR?
What is Vite?
How does Vite use native ES modules?
What is "no-bundle development"?
What is a plugin in Vite?
What is Turbopack?
Why is Turbopack written in Rust?
What is the main advantage of Turbopack over other bundlers?
What does the term "incremental bundler" mean?
What does "lazy compilation" mean?
How does Turbopack cache build results?
What is esbuild?
What language is esbuild written in?
What is npx?
What is npm?
Why is npm installed together with Node.js?
How do you initialize a project with npm?
What does node_modules store?
What is the npm registry?
How do you install a package?
How does a local install differ from a global one?
What does npm run do?
How do you run a script by name?
What are dependencies?
What are dev dependencies and how do they differ from regular dependencies?
How does npx differ from npm?
What is Yarn?
How does Yarn differ from npm?
Why is Yarn considered fast?
What is pnpm?
How does pnpm differ from npm and Yarn?
Why is pnpm considered more performant?
How does pnpm save disk space?
What is .pnpm-store?
What are pnpm workspaces?
Why is pnpm most often used in monorepos?
What is the store in pnpm?
What are the main CSS preprocessors?
What are the advantages of preprocessors over plain CSS?
What does a preprocessor do during compilation?
What are variables in preprocessors?
What is "interpolation" in SCSS?
What is nesting in preprocessors?
Why is excessive nesting an anti-pattern?
What are functions in SCSS?
What does @if do in SCSS?
What does the @extend directive do?
What is a CSS postprocessor?
How does a postprocessor differ from a preprocessor (SASS/LESS)?
What does a postprocessor do at build time?
What problems do postprocessors solve in modern frontend?
What is PostCSS?
How does PostCSS process CSS files?
When is PostCSS used together with preprocessors?
Why is Tailwind called a utility-first framework?
How does Tailwind integrate with PostCSS?
What does the JIT (Just-In-Time) compiler do in Tailwind?
What is the advantage of Tailwind over classic CSS?
Why does Tailwind speed up layout work?
How does Tailwind help maintain a unified design?
How does Tailwind help with UI consistency?
What is a utility class?
What is ESLint? Why is ESLint needed?
How is ESLint different from Prettier?
What does the term "static code analysis" mean?
How does ESLint improve code quality?
What is an ESLint rule?
What is a plugin in ESLint?
What is AST when writing a plugin, and how do you work with it?
What is Prettier? Why is Prettier needed?
How is Prettier different from ESLint?
Can Prettier check for code errors?
What does Prettier do to code?
Why is Biome needed?
Why is Biome faster than its alternatives?
What is unit testing?
Why write unit tests?
How do unit tests help with refactoring?
What is "Test Driven Development (TDD)"?
What is Jest?
How to write a basic test in Jest?
How to describe expectations in a test?
What is a mock function in the context of tests?
What is snapshot testing?
Why are snapshots often considered an anti-pattern?
What is screenshot (visual) UI testing?
How does visual testing differ from functional testing?
What is the goal of screenshot testing?
What does a visual regression test do?
Why is it especially useful in large projects?
Why can visual tests be flaky?
What tools are used for visual testing?
What is component testing?
How does component testing differ from E2E?
Why is it important for tests to be isolated?
What is snapshot testing of components?
Why are snapshots often considered an anti-pattern?
What is React Testing Library?
What types of selectors does RTL provide?
What is E2E testing?
How do E2E tests differ from unit tests?
What is the optimal ratio between unit, integration and E2E tests?
Why are E2E tests often flaky?
What popular tools are used for E2E testing of frontend applications?
What does an E2E test look like at the code level?
What is the "page object pattern"?
What does "mocking" mean in E2E tests?
When should you mock the API, and when not?
Why shouldn't there be many E2E tests?
How does performance affect SEO?
What does "rendering optimization" mean?
What are the main metrics that affect UX?
What is the critical rendering path (CRP)?
What is time-to-interactive (TTI)?
What is first contentful paint (FCP)?
What is largest contentful paint (LCP)?
What is first input delay (FID)?
What is cumulative layout shift (CLS)?
What is a performance budget?
What tools are used for analysis?
What does Lighthouse do?
What does Web Vitals do?
How to use Chrome DevTools for measurements?
What does the Performance tab do?
What does the Network tab show?
What does the Memory tab show?
What is profiling (code profiling)?
How to use Performance Insights in Chrome?
What does the Core Web Vitals API do?
Why is it important to reduce initial load?
What is code splitting?
Why is it important to remove unused code?
What does minification do?
How does CSS affect performance?
What does reflow (layout) do?
What does repaint do?
Why is the Virtual DOM faster than the regular DOM?
Why are images a major cause of slow loading?
What is Storybook?
What is Storybook used for?
Why is Storybook called a "UI playground"?
What is a UI catalog?
How can Storybook help with UI screenshot testing?
Why implement analytics in web applications?
How does analytics differ from performance metrics?
What is event-driven analytics?
Why is it important to collect metrics on the client?
What is Google Analytics (GA)?
What three core metrics make up Core Web Vitals?
What is FID (First Input Delay)?
What is CLS (Cumulative Layout Shift)?
What does a feature flag do?
What is error analytics?
How do you track errors on the frontend?
SEO interview questions
What is SEO?
What goals does SEO optimization pursue?
What is ranking?
What is organic traffic?
What affects a site's ranking position in search results?
What is indexing?
What is website crawling?
What does a search crawler (bot, spider) do?
What is semantic markup?
Why is semantic markup needed?
How does semantics affect accessibility?
Why do search engines analyze HTML structure?
What is a "meaningful document structure"?
What new semantic tags appeared in HTML5?
Why is it important to use h1-h6 headings correctly?
Can you use multiple h1 tags on a page?
How does semantic markup help navigation?
Why is alt important for SEO and accessibility?
Why is content considered the foundation of SEO?
What is quality content?
What does content uniqueness mean?
What is on-page SEO?
How does on-page SEO differ from off-page SEO?
Why is on-page SEO important for site ranking?
What goals does on-page optimization pursue?
How does HTML structure affect SEO?
What is an SEO-friendly page structure?
What mistakes are most commonly made in on-page optimization?
What is the <title> tag? What role does title play in SEO?
What is meta description?
How does heading structure affect SEO?
What does the term "content optimization" mean?
What is an SEO-friendly URL?
What should an ideal URL look like?
What is a canonical URL?
How does sitemap.xml help search engines index URLs?
How does loading speed affect search ranking positions?
What are Core Web Vitals?
What metrics are included in Core Web Vitals?
What is LCP (Largest Contentful Paint)?
What is CLS (Cumulative Layout Shift)?
What is FID (First Input Delay)?
What is PageSpeed Insights?
How to use Lighthouse for an audit?
Why does responsive design matter for SEO?
What are robots meta tags (index, noindex)?
How to use schema.org to improve a snippet?
What is Open Graph and why is it needed?
How do OG tags affect click-through rate on social media?
What is microdata markup?
Why is it important to declare the page language in HTML?
What is off-page SEO?
How does off-page SEO differ from on-page SEO?
Why is off-page SEO important for ranking?
Why do search engines take external signals into account?
What metrics indicate successful off-page promotion?
What is link building?
What is a "backlink" (inbound link)?
What is crowd marketing?
What is Technical SEO?
How does technical SEO differ from on-page and off-page SEO?
How can technical errors hinder SEO?
How do search engine crawlers scan a site?
What does the term "crawlability" mean?
What is "indexability"?
Where should the robots.txt file be located?
What does the Disallow directive do in robots.txt?
What does the Allow directive do?
What does the User-agent directive do?
What does the User-agent directive do?
What does the `<meta name="robots" content="noindex">` meta tag do?
What is "URL canonicalization"?
What is sitemap.xml?
What is performance in the context of SEO?
Why does site speed affect SEO?
When did Google officially make speed a ranking factor?
How does a slow site affect user experience?
Why is performance important for conversion?
What is "Core Web Vitals"?
Which metrics make up Core Web Vitals?
What is LCP (Largest Contentful Paint)?
What is FID (First Input Delay)?
What is CLS (Cumulative Layout Shift)?
How do Core Web Vitals affect ranking?
Next.js interview questions
What is caching in Next.js?
How server components (rsc) work in Next.js
How does app differ from pages in Next.js?
What are API Routes in Next.js?
What are Server Actions in Next.js?
Font optimization (next/font) in Next.js
How incremental static regeneration (ISR) works in Next.js
Parallel and sequential data fetching in Next.js
Layouts and templates in Next.js
middleware in Next.js
Configuring Next.js (next.config.js)
Key features of Next.js
How static site generation (SSG) works in Next.js
How client-side rendering (CSR) works in Next.js
Streaming and loading UI in Next.js
Error handling in Next.js
Server and client component patterns in Next.js
How to configure revalidation?
Internationalization (i18n) in Next.js
Deploying Next.js applications
What is Next.js and why use it
What is Next.js and what problem does it solve?
What are the main features Next.js provides out of the box?
What is SSR and why is it needed?
What is SSG and when is it used?
What is ISR and what problem does it solve?
Why is Next.js considered a fullstack framework?
Can Next.js be used only as a frontend?
In which cases is Next.js overkill?
Routing in Next.js (file-based routing)
How does project structure affect routing in Next.js?
Which folders are required?
Can you use Feature-Sliced Design in Next.js?
Dynamic routes and dynamic segments in Next.js
Next/link and navigation in Next.js
How does app/layout.tsx work in Next.js?
What is template.tsx in Next.js?
How does global-error.tsx work in Next.js?
What does not-found.tsx do in Next.js?
How server-side rendering (SSR) works in Next.js
What is the key idea of routing in Next.js?
What types of routing exist in Next.js?
What is the difference between app and pages router in Next.js?
How is a route formed in the app router?
What are route segments in Next JS?
What is not-found.tsx in Next.js?
What is a dynamic route in Next.js?
What is `generateStaticParams`?
What does the Link component do in Next JS?
How does prefetch work in Next.js?
How does useRouter work in app router?
What is SSG in Next JS?
What is SSR in Next.js?
What is ISR in Next.js?
What is CSR in Next.js?
What is hydration?
What is streaming rendering?
How is Suspense related to rendering?
What are server components in Next.js?
Data fetching in Next.js
What are client components in Next.js?
Which tasks are best solved with server components?
What tasks are best solved with client components?
What is hybrid rendering in Next.js?
What does the "use client" directive do?
How can a server component pass data to a client component?
What ways of fetching data exist in Next.js?
How does Next.js differ from React in terms of data fetching?
Where does data fetching happen in Next.js - on the server or the client?
What are Server Components in Next.js?
Can await fetch be done directly in a component?
How do Server Components cache data?
Where are API Routes created?
What caching levels exist?
What problem do Server Actions solve?
How are Server Actions different from API Routes?
What does the "use server" directive mean?
How does Next.js load data on the server?
Image optimization (next/image) in Next.js
What is the difference between client-side and server-side data loading?
What problems does server-side data loading solve?
What is `getStaticProps`?
What is ISR?
How does revalidate work?
Can fetch be used directly in a Server Component?
What caching options does `fetch` have?
What caching levels are there in Next.js?
What are API Routes?
What are Server Actions?
What is a layout in Next.js?
Authentication patterns in Next.js
What tasks do layout components solve?
How does layout differ from a regular React component?
How does layout affect performance?
What is a Root Layout?
What are route groups?
What is the Metadata API in Next.js?
What is static metadata?
What is dynamic metadata?
How is the final <title> formed?
What is Open Graph?
What is robots metadata?
What metrics are used to measure site speed?
Environment variables in Next.js
Why does speed matter for SEO?
Why is Next.js faster than a regular SPA?
Edge runtime vs Node.js runtime in Next.js
What performance problems does CSR have?
Why does JS bundle size matter?
Why are Client Components more expensive?
What is waterfall fetching?
Nuxt.js interview questions
What is Nuxt.js and how does it differ from Vue.js?
How do auto-imports work in Nuxt?
What are plugins in Nuxt?
What are rendering modes in Nuxt (SSR, SSG, SPA, Hybrid)?
What is the difference between useFetch and useAsyncData in Nuxt?
What are layouts in Nuxt?
What is middleware in Nuxt and how to use it?
What are composables in Nuxt?
How to create API routes in Nuxt?
Redux interview questions
Redux vs context API
Redux Thunk vs Redux Saga - what is the difference?
What are selectors in Redux?
Redux toolkit
What is Redux?
Redux middleware
Node.js interview questions
What is libuv and how does it enable async i/o in Node.js?
How the Event Loop works in Node.js
What is error-first callback pattern?
Error handling patterns in Node.js
What are child processes in Node.js?
What are worker threads in Node.js?
What are the key security best practices in Node.js?
What are streams in Node.js?
What is middleware in Express.js and how does it work?
What is the cluster module in Node.js?
What is PM2 and how to manage Node.js processes in production?
How to work with environment variables in Node.js?
What is the difference between process.nextTick() and setImmediate()?
Synchronous vs asynchronous code in Node.js
What is the difference between promise.all and promise.allsettled?
What is eventemitter in Node.js?
What is a buffer in Node.js?
Why are events asynchronous in Node.js?
How does the HTTP module work in Node.js?
How to use the Crypto module in Node.js for hashing and encryption?
What is Node.js?
Node.js vs the browser
Working with a server
What is non-blocking I/O?
Why is Node.js considered single-threaded?
Advantages and disadvantages of being single-threaded
What are the pros and cons of Node.js being single-threaded?
Packages and package.json
What is package.json and how does npm work?
What is package-lock.json?
What is npm?
What is the Node.js runtime made of?
V8 and its role
libuv and its role
Event loop in Node.js
What are native modules in Node.js?
Garbage collection in V8
What phases does the Event Loop consist of?
Heap and stack in Node.js
CommonJS vs ES Modules
What is process?
Environment variables
The global object global
How do Timers and scheduling work in Node.js?
Why is Node.js called a single-threaded environment?
Parallelism vs asynchrony
Blocking and non-blocking code
The importance of parallelism for scaling
worker_threads in Node.js
How are threads different from processes?
How do you pass data between threads?
What is SharedArrayBuffer?
What does the message event do in a worker?
What does the child_process module do?
Parent and child process
What is the cluster module?
How does cluster help scale an application?
What is IPC (inter-process communication)?
Vertical vs horizontal scaling
What does PM2 do for scaling?
What does round-robin scheduling do?
What is a module in Node.js?
What does the term "CommonJS" mean?
What is promisification?
What does require() do?
What does the module object do?
What is a "circular dependency"?
module resolution
module resolution
ESM vs CommonJS
ESM vs CommonJS
Named vs default export
Dynamic import import()
What is a "core module" in Node.js?
What does the fs module do in Node.js?
How do you read a file in Node.js?
readFileSync and its danger
How do you write data to a file?
How do you create a directory in Node.js?
What does "I/O" mean in the context of Node.js?
Why are I/O operations considered slow?
Why does Node.js implement "non-blocking I/O"?
Streams and I/O operations
What is Buffer in Node.js?
Buffer vs array
What does fs.watch() do?
Why is chunked I/O more efficient?
Combining streams and buffers for performance
Why are streams the foundation of I/O?
Stream types
What is a Readable stream?
What is a Writable stream?
What is a Duplex stream?
What is a Transform stream?
What does pipeline() do in the stream module?
How do you chain several streams together?
What is backpressure?
How does backpressure arise?
How does Node.js support the Web Streams API?
What is an event in the context of Node.js?
What does the event model look like?
What is the events module?
How do you subscribe to an event?
What does the emit() method do?
What does the on() method do?
What does once() do?
An HTTP server without frameworks
How do you handle a request inside createServer()?
How do you send an HTTP request from Node.js?
How does HTTPS differ from HTTP?
What is CORS?
What is a preflight request?
WebSocket's bidirectionality
What is HTTP/2?
What is Express.js?
What is middleware in Express.js?
request and response
What is a route in Express?
What does express.Router() do?
Middleware order
What are controllers in Express applications?
Business logic and controllers
Express's place in the modern world
What is NestJS?
What is a module in NestJS?
What is a controller in NestJS?
What is a provider?
The main parts of an application
What does the IoC container do in NestJS?
Where should you move business logic out of controllers?
What are Singleton providers?
Circular dependency between modules
What are global providers?
What is Middleware in NestJS?
What is a Guard?
What is a Pipe?
What is a DTO?
DTO validation
What is an Exception Filter?
What is an Interceptor?
What are microservices in NestJS?
How to detect and prevent memory leaks in Node.js?
What are the most common design patterns in Node.js?
Express.js interview questions
What is middleware in Express.js and how does it work?
How to handle file uploads in Express.js with Multer?
How to serve static files and improve performance in Express.js?
How to secure an Express.js application?
How to test an Express.js application?
What are the req and res objects in Express.js?
Express.js vs Fastify vs Koa — which to choose?
Route parameters and query strings in Express?
What is Express router and how to use it for modular routing?
How to build a REST API with Express.js?
How to implement API versioning in Express.js?
What are the different types of middleware in Express.js?
How to validate request data in Express.js?
How to handle async/await in Express.js route handlers?
How to handle errors in Express.js?
How to use template engines in Express.js?
How does session management work in Express.js?
What is CORS and how to configure it in Express.js?
How to optimize Express.js application performance?
How to implement caching in Express.js for better performance?
How to implement logging in Express.js (Morgan, Winston)?
How to structure a large Express.js application?
What are the best database integration patterns in Express.js?
How to integrate WebSocket with Express.js?
NestJS interview questions
How to implement caching strategies in NestJS?
What are lifecycle hooks in NestJS?
What are providers and how does dependency injection work in NestJS?
What are Dynamic Modules in NestJS and when to use them?
What is middleware in NestJS and how does it differ from guards?
How do Microservices work in NestJS?
What are modules in NestJS and how do they work?
How to manage configuration in NestJS with configmodule?
What are controllers in NestJS?
What are dtos and how does validation work in NestJS?
How to create and use custom decorators in NestJS?
How to document a NestJS API with Swagger?
What are interceptors in NestJS?
What are pipes in NestJS?
What are exception filters in NestJS?
How to implement authentication with Passport in NestJS?
How to implement Role-Based Access Control (RBAC) in NestJS?
How does NestJS integrate with TypeORM?
How to implement WebSocket Gateways in NestJS?
How to implement queue processing with Bull in NestJS?
What is CQRS pattern and how to implement it in NestJS?
How to test a NestJS application?
Python interview questions
Java interview questions
Go interview questions
Algorithms interview questions
What is recursion?
What is an algorithm?
What properties should an algorithm have?
What does "discreteness" of an algorithm mean?
What are the "input data" and "output data" of an algorithm?
What is an algorithm flowchart?
What are the main blocks used in flowcharts?
What is a linear structure of an algorithm?
What are nested conditions?
What is a pre-condition loop?
What is a post-condition loop?
What types of algorithms exist by structure?
What is a linear algorithm?
What is a branching algorithm?
What does time complexity mean?
What does space complexity mean?
Why is it important to estimate complexity?
What does asymptotic complexity mean?
What is Big O notation?
What does "worst case" mean (worst case)?
What is the base case of recursion?
What is the recursive case?
Why is it important for any developer to know algorithm basics?
What does "algorithm complexity" mean?
What does an "order-of-growth estimate" mean?
Why are constants and lower-order terms often ignored?
What is a function's "growth rate"?
What does O(n) - linear complexity - mean?
What does O(n²) - quadratic complexity - mean?
What does "worst case" mean?
How is an algorithm's memory usage measured?
How does creating new arrays affect complexity?
What is the "call stack" in the context of memory?
How does recursion affect space complexity?
What does "recursion depth" mean?
What is the complexity of bubble sort?
What is the complexity of binary search?
What is sorting?
What is the complexity of the fastest sorting algorithm? Why can't it be made faster?
What is a "key" in sorting?
What are exchange sorts (exchange sorts)?
What is selection sort (selection sorts)?
What is insertion sort (insertion sorts)?
What is merge sort (Merge Sort)?
How does BubbleSort work?
How does quicksort (Hoare partition) work?
What is search used for?
What is linear search?
What is binary search?
What is the complexity of binary search?
Why is the algorithm called "binary"?
Why does binary search require a sorted array?
What does a binary search tree (BST) do?
What is exponential search (exponential search)?
What is the time complexity of index access?
What is the complexity of inserting an element into the middle of an array?
Why is appending to the end of an array more efficient?
What does "dynamic array" mean?
What is amortized complexity?
How to iterate over an array with a loop?
How to find the maximum element of an array?
How to reverse an array?
How to find an element in an array using linear search?
What is the "sliding window" technique?
How to count a string's length without built-in methods or properties (length)?
How to implement naive substring search?
What is a suffix array?
What does a tree consist of?
What is a node (node)?
What is the height of a tree?
What is a binary tree?
What are the main types of tree traversal?
What does postorder traversal (postfix tree traversal) do?
What does preorder traversal (prefix traversal) do?
What does level-order traversal (traversing a tree by levels) do?
What does the stack do during traversal without recursion?
What is Depth-first search (DFS)?
What is Breadth-First Search (BFS)?
How does the search algorithm work with a binary tree?
Why is tree balancing needed?
What does a graph consist of?
What is a weighted graph?
What is a directed graph?
How can a graph be stored in memory?
What does the BFS algorithm do on graphs (Breadth-First Search)?
What does the DFS algorithm do on graphs (Depth-First Search)?
What does the queue do in BFS on graphs?
What does the stack do in DFS on graphs?
What is topological sorting in graphs?
How does Dijkstra's algorithm work on graphs?
What does the Bellman-Ford algorithm do on graphs?
What does the Floyd-Warshall algorithm do on graphs?
What is a greedy algorithm?
What does a locally optimal choice mean in a greedy algorithm?
What does a globally optimal solution mean in a greedy algorithm?
What does 'greedy choice criterion' mean?
What is "optimal substructure" in a greedy algorithm?
When is a greedy algorithm inefficient?
What problems are classically solved with a greedy algorithm?
How is the classic coin change problem solved using a greedy algorithm?
What is dynamic programming (DP)?
What is the difference between DP and a greedy algorithm?
What does "overlapping subproblems" mean in dynamic programming?
What is "memoizing intermediate results" needed for?
What is tabulation in DP?
What does "state" mean in DP?
Why is it important to choose the state correctly in dynamic programming?
How is the classic "knapsack problem" solved in dynamic programming?
What are the main types of problems combinatorics solves?
What does an "arrangement" mean in combinatorics?
What is a combination in combinatorics?
How to calculate the number of permutations of n elements?
How to calculate the number of combinations of n choose k?
What is Pascal's triangle?
What does number theory study?
How to calculate the sum of divisors of a number?
Data Structures interview questions
What is a data structure?
Why are data structures important in algorithms?
What are the main types of data structures?
Why does the choice of data structure affect an algorithm's O(n) complexity?
How to evaluate the efficiency of a data structure?
What is time complexity?
What does "access time" mean in a data structure?
What does "insertion time" mean?
What is an array as a data structure?
How does an array differ from a list?
How is the memory address of an array element calculated?
What does "contiguous placement of elements" in memory mean?
How does a static array differ from a dynamic array?
What happens when an array goes out of bounds?
What is the time complexity of accessing an element in an array?
What is the complexity of inserting into the middle of an array?
What is the time complexity of deleting from an array?
What does amortized complexity mean?
What is a multidimensional array?
What is a linked list?
How does a linked list differ from an array?
What types of linked lists exist?
How are nodes connected to each other in a list?
What is the complexity of accessing an element by index?
What is the complexity of inserting at the beginning of a list?
What is the complexity of inserting at the end of a list?
What is the complexity of deletion from the middle of a list?
Why is a linked list efficient for frequent insertions/deletions?
How is a linked list stored in memory?
What is a singly linked list (singly linked list)?
What is a circular linked list (circular linked list)?
In which tasks is it better to use a list instead of an array?
What is head and tail of a list?
What is a stack as a data structure?
What is the LIFO principle in a stack?
How does a stack differ from a queue?
Why is a stack convenient for recursive computations?
What does "call stack" mean in programming?
In which tasks is a stack most often used?
What is a queue?
What principle underlies how a queue works?
What does "FIFO" mean?
How does a queue differ from a stack?
What is the time complexity of inserting into a queue?
What is the time complexity of removing from a queue?
How does implementing a queue on a linked list differ from implementing it on an array?
What is "element shifting" and why is it inefficient?
What is a double-ended queue (deque)?
What operations does a deque support?
What is a priority queue?
How is a queue used in BFS (breadth-first search)?
What tasks is a queue often used to solve?
What is a hash table?
What is the idea behind hashing?
How does a hash table store data?
What are a key and a value in a hash table?
Why does a hash table provide fast access to data?
What is a "bucket" in the context of a hash table?
What is a collision in a hash table? Why are they inevitable?
Why is a perfect hash function impossible in practice?
Why is it important for a hash function to be fast?
What does the modulo (%) operation do in hashing? How is it related to indices?
What is the complexity of inserting an element into a hash table?
What is the complexity of accessing an element in a hash table?
What is the complexity of removing an element from a hash table?
In which tasks are hash tables most effective?
What is a tree as a data structure?
What is a node (node) in a tree?
What is an edge (edge) in a tree?
What is the root of a tree (root)?
What is a leaf (leaf)?
What are a parent and a child (parent / child)?
What is the height of a tree (height)?
What is the depth of a node (depth)?
How are the height and depth of a tree related?
What is a binary tree?
What is a binary search tree?
What is tree balancing?
What is the time complexity of searching for a node in a binary tree?
What is breadth-first tree traversal (BFS)?
What is depth-first tree traversal (DFS)?
What is tree density?
What is an AVL tree, and what makes it balanced?
What is a trie (prefix tree)?
What is a graph?
What is a vertex in a graph?
What is an edge in a graph?
What does "adjacency" of vertices in a graph mean?
What is the size of a graph?
What is a directed graph?
What is an undirected graph?
What is a weighted graph?
What does edge weight mean?
What is a loop in a graph?
What are the ways to store graphs?
What is an adjacency matrix?
What does breadth-first search (BFS) do?
What does depth-first search (DFS) do?
What is topological sorting? For which graphs is it possible?
What does the Bellman-Ford algorithm do?
Networking & Internet interview questions
What is a computer network?
What types of computer networks are there?
What is LAN?
What does the term "network topology" mean?
What types of topologies exist?
What is point-to-point (P2P)?
What is network bandwidth?
What is a client-server network?
What is IPv4?
What parts does an IPv4 address consist of?
What is a subnet mask?
What is a broadcast address?
What are private IP addresses?
What is a subnet?
What is IPv6?
What is Ethernet?
What is a MAC address?
How is a MAC address structured?
What is the OSI model?
Name all the layers of the OSI model.
What is the main function of the OSI physical layer?
What does the OSI data link layer do?
What does the OSI network layer do?
What does the OSI transport layer do?
What does the OSI presentation layer do?
What does the OSI application layer do?
What is the TCP/IP model?
How does OSI differ from TCP/IP?
Name the layers of the TCP/IP model.
Which TCP/IP model layers relate to the OSI application layer?
Which OSI model layers are combined in the TCP/IP network access layer?
At what OSI layer does IP operate?
At what layer does TCP operate?
Why isn't the OSI model used directly in real networks?
Why is TCP/IP a practical model?
What is a protocol stack?
Why does dividing into layers simplify how networks work?
What is the physical layer of the OSI model?
What tasks does the physical layer solve?
What data is transmitted at the physical layer?
What units of measurement are used at the physical layer?
What is bit-level transmission?
What is signal encoding?
What is interference?
How does the physical layer deal with interference?
What is twisted pair?
What is the data link layer of the OSI model?
What tasks does the data link layer solve?
What place does the data link layer occupy in the OSI model?
How does the data link layer differ from the physical layer?
What is a frame?
What is the MAC sublayer?
What is the LLC sublayer?
Where is MAC implemented: in hardware or software?
What is a MAC address?
How long is a MAC address?
What is a multicast MAC address?
What is a broadcast MAC address?
Why are MAC addresses needed?
What is an Ethernet frame?
What fields does an Ethernet frame consist of?
Why does a minimum frame size exist?
What errors does the data link layer detect?
What is a network switch (switch)?
What is frame forwarding?
What is a VLAN?
What tasks does the network layer solve?
What types of addresses are used at the network layer?
What data is transmitted at the network layer?
What is a packet?
Why is the network layer considered "routable"?
What protocols work at the network layer?
How does IPv4 differ from IPv6?
What is the size of an IPv4 address?
In what form is an IP address stored?
What is a network address?
What is a host address?
What is a broadcast address?
How does a mask separate the network from the host?
What is a subnet?
How do you determine the size of a subnet?
What are private IP addresses?
What is routing?
What does a router do?
What is a route?
What is static routing?
Pros and cons of static routing
What is dynamic routing?
When is dynamic routing used?
What is the transport layer of the OSI model?
What tasks does the transport layer solve?
What protocols operate at the transport layer?
What is the transport layer responsible for in an end-to-end connection?
What is a segment (segment)?
Why is the transport layer critical for applications?
What is a port?
What is the range of TCP/UDP ports?
What is a socket?
Can multiple applications use the same port?
What guarantees does TCP provide?
What guarantees does UDP provide?
Why is UDP called "unreliable"?
What is a TCP segment?
What fields make up a TCP header?
What is a sliding window?
How does TCP detect segment loss?
What fields make up a UDP header?
What happens when a UDP packet is lost?
What is multiplexing at the transport layer?
What is demultiplexing?
What is the application layer of the OSI model?
What tasks does the application layer solve?
Which protocols belong to the application layer?
Why is the application layer closest to the user?
What is client-server architecture?
What is a request (request)?
What is stateless interaction?
What is stateful interaction?
What is HTTP?
What is FTP?
What is SMTP?
What is POP3?
What is IMAP?
What is DNS?
What is WebSocket?
What is HTTP?
What port does HTTP run on by default?
What is an HTTP request?
What is an HTTP response?
What is the difference between HTTP/1.1 and HTTP/2?
What is an HTTP method?
What is GET used for?
What is POST used for?
What is PUT used for?
What is PATCH used for?
What is DELETE used for?
What are HTTP headers?
What is an HTTP status code?
What classes of HTTP codes exist?
What is HTTPS?
What is TLS?
What is a cookie?
Where are cookies stored?
What is an HttpOnly cookie?
What is REST?
What is DNS?
What problem does DNS solve?
At which OSI layer does DNS operate?
What is a domain name?
What is a DNS server?
What is a zone (DNS zone)?
What is DNS resolve?
What is a DNS record?
What is an A record?
What is CNAME?
What is an NS record?
What is a TXT record?
What is TTL in DNS?
What is DNS cache?
What protocol does DNS use?
What is DNSSEC?
What is network security?
What does the CIA triad mean?
Which OSI layers does network security affect?
Which OSI layers does network security affect?
What is a security policy?
What is zero trust?
What types of network attacks are there?
What is man-in-the-middle (MITM)?
What are flooding attacks?
What is Port Security?
What is IP spoofing?
What is ACL?
How does a standard ACL differ from an extended ACL?
What is a firewall?
What types of firewall are there?
What is IDS?
What is IPS?
What attacks are typical for L7?
What is SQL Injection?
What is CSRF?
What is WAF?
What is authentication?
What is authorization?
Why is encryption needed in networks?
What is DDoS?
What is rate limiting?
Design Patterns interview questions
What are grasp patterns
What is the Abstract Factory pattern?
What is Proxy design pattern?
MVC (model-view-controller) and MVP (model-view-presenter) design patterns
What is the Singleton pattern?
What key problems does the Singleton pattern solve?
How does a lazy Singleton differ from an eager one?
Why is Singleton often called an "anti-pattern"?
How does Singleton violate the single responsibility principle (SRP)?
When is Singleton actually justified?
What is the Factory Method pattern?
How does Factory Method differ from a plain constructor?
How does Factory Method contribute to system extensibility?
What is the difference between Factory Method and Abstract Factory?
How is Factory Method related to the open/closed principle (OCP)?
How does Abstract Factory differ from Factory Method?
How does Abstract Factory promote loose coupling between components?
Why is Abstract Factory often used together with Dependency Injection?
What are the weaknesses of Abstract Factory?
What is the Builder pattern?
How does Builder help when creating complex objects?
What does "director" mean in the Builder pattern?
How does Builder differ from Chain of Responsibility?
What drawbacks does the Builder pattern have?
What is the Prototype pattern?
When is the Prototype pattern used?
When can Prototype be dangerous?
What is the main purpose of the Adapter pattern?
What types of adapters exist?
What is the difference between the Adapter and a plain wrapper class?
When should you use the Adapter pattern in a project?
What does the Bridge pattern do?
What is the point of separating abstraction and implementation in the Bridge pattern?
What advantages does the Bridge pattern give when testing code?
When can the Bridge pattern be overkill?
What problem does the Composite pattern solve?
Why is it important for objects and containers to share a common interface?
Why is Composite often used in file systems?
What is the advantage of Composite for recursive data structures?
What drawbacks does the Composite pattern have?
What is the essence of the Decorator pattern?
What is the advantage of dynamically adding functionality?
What do Decorator and Wrapper have in common?
What drawbacks does the Decorator pattern have?
What is the essence of the Façade pattern?
How does Façade differ from Adapter?
How does the Façade pattern help reduce coupling between modules?
Why does Façade make testing and isolating components easier?
What happens if a facade becomes too "fat"?
What problem does the Flyweight pattern solve?
Why can Flyweight improve performance?
When does using Flyweight become inefficient?
What does the Proxy pattern do?
How does "Proxy" differ from "Decorator"?
In what situations is Proxy especially useful?
What challenges can arise with the Proxy pattern?
What is Adapter design pattern?
How is a request passed along a chain of handlers?
decorator pattern
What are the pros and cons of the Chain of Responsibility?
In which cases is it appropriate to apply this pattern?
What is Module design pattern?
What does the Command pattern do and why is it needed?
How does the Command pattern facilitate undo/redo functionality?
What classes are typically involved in implementing Command?
What is the core idea of the Interpreter pattern?
When is using the Interpreter pattern justified?
Why is this pattern rarely used in practice?
What is the purpose of the Iterator pattern?
How does an iterator simplify traversal of complex data structures?
What is the difference between an external and an internal iterator?
How does it reduce coupling between objects?
What are Mediator's downsides?
When does Mediator lead to architectural complexity?
What does the Memento pattern do?
What three roles are involved in Memento?
What's the difference between Memento and Command when implementing rollback?
How do you store a change history using Memento?
What is the essence of the Observer pattern?
What problems does Observer solve?
What does the State pattern do and when is it useful?
How does State differ from Strategy?
How does State simplify large conditional constructs (if-else/switch)?
What classes are involved in implementing the pattern?
What does the Strategy pattern do and why is it needed?
How does Strategy help get rid of many conditional operators?
How does Strategy increase a system's flexibility?
What is the idea behind the Template Method pattern?
What is the Visitor pattern used for?
How does Visitor help add new operations without modifying classes?
What classes are involved in Visitor?
What does the Inversion of Control (IoC) principle mean?
Observer pattern
What does "dependency inversion" (inversion) mean?
What is Strategy design pattern?
How does IoC help reduce coupling between components?
What is Command design pattern?
Why should high-level modules not depend on low-level modules?
How does IoC help build modular systems?
How does DI differ from ordinary manual dependency injection?
What types of dependency injection exist?
How does DI help with unit testing?
What does "container-based DI" mean?
Why can incorrect DI lead to "dependency hell"?
Why can incorrect DI lead to "dependency hell"?
How does DI increase a system's flexibility when scaling?
What is a dependency container?
What does the "lifetime" of dependencies (singleton, scoped, transient) mean?
How to avoid circular dependencies in a container?
Why is it important to manage the lifetime of services?
What is layered architecture?
What main layers does traditional architecture include?
What are the advantages of layered architecture?
What is the "presentation layer"?
What does the "business logic layer" do?
How do layers interact with each other?
Why is it important to limit dependencies between layers?
Give examples of typical layers in a web application
How to implement DI in a layered architecture?
What is the main idea of the MVC pattern?
What are the responsibilities of Model, View, and Controller?
How does MVC provide separation of concerns?
What are the benefits of MVC for UI applications?
Why does MVC simplify testing?
What are the common mistakes when implementing MVC?
Tell me about the MVP approach.
How does MVVM differ from MVC?
What does the ViewModel do in MVVM?
How does the ViewModel provide two-way data binding?
What does the Presenter do in MVP?
Why is MVVM considered a reactive approach?
What does "unidirectional data flow" mean?
What is microservices architecture?
How do microservices differ from a monolith?
What problems does the microservices approach solve?
What does the "one business function, one service" principle mean?
What is an API Gateway?
How do microservices interact with each other?
What is a "bounded context" in microservices architecture?
Why is it important to isolate the database for each microservice?
What are the downsides of the microservices approach?
When are microservices not justified?
What does "loose coupling" mean between services?
What does "high cohesion" mean inside a service?
How to determine the boundaries of a microservice?
Why is REST not always the best choice for microservices?
When should you use gRPC?
What is event sourcing?
What is idempotency and why is it needed?
How is the data consistency problem between services solved?
Why is direct access to another service's database an anti-pattern?
What does an orchestrator (Kubernetes, Nomad, ECS) do?
What anti-patterns do you know when working with microservices?
What is a "Distributed Monolith"?
What key elements are part of EDA (publisher, subscriber, event bus)?
What does "event sourcing" mean?
What does a message broker (Kafka, RabbitMQ) do?
How does EDA improve scalability?
Why does EDA reduce coupling between services?
What does "idempotency" mean in the context of events?
How does EDA differ from request-response architecture?
How to store events in an event store?
What problems arise from redelivering events?
What does Clean Architecture represent?
How are the layers structured in Clean Architecture?
What does the "dependency rule" mean?
How is DI implemented in Clean Architecture?
How does Clean Architecture differ from Layered Architecture?
Why shouldn't the UI depend on business logic?
What is Domain-Driven Design (DDD)?
Why is DDD especially well suited to complex domains?
What is model in the context of DDD?
How does DDD help avoid "anemic" models?
How does DDD affect the project's architecture?
How does DDD relate to the SOLID principles?
What is strategic design in DDD?
What does bounded context (a limited context) mean?
What is an entity?
What is a repository?
What does the term "Ubiquitous Language" mean?
What is an aggregate in DDD?
Why should aggregates be small?
What is a domain event (an event in the domain)?
What is an "Anemic Domain Model"?
Why does DDD help define microservice boundaries?
Principles & SOLID interview questions
SOLID principles
What is Liskov Substitution Principle (LSP)?
DRY (don't repeat yourself)
What does the Single Responsibility Principle mean?
How do you determine that a class or module violates SRP?
KISS (keep it simple, stupid)
YAGNI (you aren't gonna need it)
Why does SRP simplify code maintenance?
How is SRP related to the concepts of "cohesion" and "coupling"?
Give an example of an SRP violation
Give an example of a class that follows SRP
How does SRP improve application modularity?
What does the Open/Closed Principle mean?
What is Single Responsibility Principle (SRP)?
How does OCP help avoid bugs when making changes?
What is Open-Closed Principle (OCP)?
How do you implement OCP through inheritance?
How do you implement OCP through composition?
Why is OCP closely tied to interfaces?
Why does OCP reduce the number of regressions?
Why does OCP reduce coupling?
How do you check whether a class follows the Liskov Substitution Principle?
Why is LSP related to inheritance?
Give an example of an LSP violation
Give an example of LSP compliance
What does the Interface Segregation Principle mean?
Why are "fat" interfaces harmful?
Give an example of an ISP violation
Why does ISP simplify refactoring?
How does ISP increase architecture flexibility?
How does ISP increase architecture flexibility?
What does the Dependency Inversion Principle mean?
Why is DIP the foundation of IoC and DI?
What does "high-level modules should not depend on low-level modules" mean?
Example of a DIP violation
Example of DIP compliance
Why does DIP increase system flexibility?
How does DIP help with testing?
What does "depend on abstraction, not on implementation" mean?
Why does DIP improve scalability?
Architecture interview questions
Microfrontend architecture
REST API design principles and best practices?
What is Microservices architecture?
What is the CAP theorem?
What is a circuit breaker?
Modular architecture
What is MVC architecture pattern?
Atomic design architecture
Feature-sliced design (FSD). must-know frontend architecture
Docker interview questions
What is Docker?
Container vs Virtual Machine: what is the difference?
What is Docker used for?
What are the main components of Docker architecture?
What is the difference between Docker and a virtual machine?
What is a container?
Docker daemon and Docker client: how do they interact?
What are Linux namespaces and cgroups in Docker?
What is an image?
What is Docker Engine?
What is containerd and its role in the Docker ecosystem?
What advantages does Docker give developers?
What is containerization?
What is a Docker registry?
How does Docker provide process isolation?
What is a Docker image?
What is a Docker image?
Docker layers and Union File System explained
How to inspect Docker image metadata?
What is a layer in a Docker image?
What does "image immutability" mean?
How to create a Docker image from a running container?
How to create a Docker image?
How do you remove a Docker image?
What are dangling Docker images and how to remove them?
What is a Docker image tag?
How to reduce the size of a Docker image?
What is a Dockerfile?
What are distroless images and what advantages do they offer?
What is the overlay2 storage driver and when to change it?
What is a base image (base image)?
What is a multi-stage build?
How does Docker merge layers in an image?
What is a container in Docker?
What is the Docker container lifecycle?
Why are containers called "lightweight virtualization"?
What happens when a container starts?
How to run a container from a Docker image?
How to list running and all Docker containers?
How to run a docker container?
How to get inside a running Docker container?
How to stop a Docker container?
docker exec vs docker attach: what is the difference?
Why is it better not to store data inside a container?
How to persist data between container runs? (junior)
How do containers exchange data with each other?
How to inspect container state, logs, and metadata?
How do you view container logs?
How to stop and remove a Docker container?
docker stop vs docker kill: what is the difference?
How to use environment variables in Docker?
How does a Dockerfile differ from an image?
What is a Docker restart policy and what options exist?
How is an image built from a Dockerfile?
How to limit container CPU and memory resources?
How to set up a health check for a Docker container?
What does "build context" mean?
How to handle signals in containers and what is the init process?
How to set the name and tag of the image being built?
What is a layer in a Dockerfile?
Why is it important to minimize the number of layers?
Why does the order of instructions in a Dockerfile matter?
What does "multi-stage build" mean?
Why should you use `alpine` images?
What is Docker Compose?
How is Compose different from a Dockerfile?
What is described in `docker-compose.yml`?
How do you rebuild images in Compose?
What is a volume in Docker?
COPY vs ADD in Dockerfile: what is the difference?
Why do you need volumes?
CMD vs ENTRYPOINT in Dockerfile: what is the difference?
Where are Docker volumes physically stored?
EXPOSE in Dockerfile vs port publishing: what is the difference?
How to mount a volume in a container?
What is a bind mount?
How does Docker build cache work and how to manage it?
How does Docker create a volume automatically?
What is a multi-stage Docker build and why use it?
How to declare a volume in docker-compose.yml?
What is BuildKit and what advantages does it provide?
What is a network in Docker?
How to build multi-platform Docker images (ARM + AMD64)?
Why can't containers see each other without a network?
What types of networks exist in Docker by default?
What does network isolation mean?
What is a bridge network?
What is the host network?
What is the none network?
What is Docker Hub?
How do containers communicate in Docker Compose?
How to manage service dependencies in Docker Compose?
What is a Docker Repository?
What does an image tag do?
What are Docker Compose profiles and how to use them?
How to pull a Docker image from a registry?
How to scale services in Docker Compose?
What does "immutable tag" mean?
How is a public registry different from a private one?
What role does a registry play in CI/CD?
Where are Docker volumes stored on the host?
How to share data between Docker containers?
How to update a Docker container without losing data?
How does Docker networking work and what network types exist?
How does Docker bridge networking work?
What is a Docker overlay network and when do you need it?
How to troubleshoot network problems between Docker containers?
Docker registry vs Docker Hub: what is the difference?
How to transfer Docker images between hosts without a registry?
How to set up a private Docker registry with Harbor?
How to debug problems in a Docker container?
How to organize log management in Docker?
How to fix 'no space left on device' on a Docker host?
How to scan Docker images for vulnerabilities?
What is rootless Docker and when to use it?
How to manage secrets (passwords, keys) in Docker properly?
What is Docker Content Trust (DCT)?
How to implement Docker container security hardening?
What is Docker Swarm?
How to perform a rolling update in Docker Swarm?
How to use Docker in a CI/CD pipeline?
Immutable infrastructure with Docker explained
Zero-downtime deployment approaches with Docker
How to live migrate a Docker container between hosts using CRIU?
Git interview questions
What is git stash and when to use it?
What is the difference between git fetch and git pull?
Difference between git reset and git revert?
What is git cherry-pick and when to use it?
What is Git?
What is git bisect?
What problem does Git solve?
What is a repository in Git?
How does Git store data?
What is a commit from Git's perspective?
How to initialize git?
What is git status used for?
What is the git add command used for?
What is git commit used for?
What is `git rm` used for?
What is git diff used for?
What is a branch in Git?
Why does Git need branches?
What is HEAD in Git?
What is the main branch of a project?
What is a feature branch?
How to delete a branch?
What is the difference between git merge and git rebase?
What is a remote repository in Git?
How does a local repository differ from a remote one?
What is `remote` in Git?
What is git clone used for?
What is git fetch used for?
What is git pull used for?
What is `git push` used for?
What is commit history in Git?
Git branching strategies (Git Flow, GitHub Flow)?
How do you view the commit history in a repository?
What is the difference between `git log` and `git status`?
What is HEAD in Git?
What does the detached HEAD state mean?
How do you move to a specific commit?
What does `git checkout <commit>` do?
How does git checkout differ from git switch?
What is the difference between HEAD~1 and HEAD^?
Can you change the commit history?
What does git rebase do to history?
When to use reset, and when revert?
What does "undoing changes" mean in Git?
What are Git tags and when to use them?
What is the working directory?
Which Git commands are used to undo changes?
What is the difference between git restore and git reset?
What is reflog and why is it needed?
What does git restore <file> do?
What does git clean do?
What does the git reset command do?
What is `git stash`?
Which changes go into stash?
How to restore changes from a stash after some time?
What is git merge?
What are Git hooks?
What is the main difference between merge and rebase?
What happens to the commit history during a merge?
What happens to the commit history during a rebase?
What is a merge conflict?
What is a conflict during rebase?
Which is easier to roll back: merge or rebase?
What does git rebase --abort do?
What happens by default with git pull?
Can git pull be configured to rebase?
What is a Git workflow?
What problems does a Git workflow solve?
What is the essence of the Feature Branch Workflow?
How are feature branches usually named?
Which branch are feature branches created from?
What is the main idea of Gitflow?
Why is the develop branch needed?
Which branch is a feature branch created from in Gitflow?
What is Trunk-Based Development?
What is the philosophy of Trunk-Based Development?
What counts as trunk?
How short should feature branches be?
What is a tag in Git?
How does a tag differ from a branch?
What is an annotated tag?
Why are tags considered immutable?
What is a release in the context of Git?
How are tags used for releases?
What does a MAJOR version mean?
What does the MINOR version mean?
What does the PATCH version mean?
What are pre-release versions?
What is CI?
What usually triggers a CI pipeline?
How does CI check code quality?
How does CI/CD affect release speed?
How does CI/CD affect stability?
What is a hotfix?
SQL interview questions
What is a database?
What is SQL? What is SQL used for?
What is a relational database?
How does a relational database differ from a non-relational one?
What is a table in a database?
What is a database schema?
What is a field?
What is an SQL query?
What are DDL, DML, DCL, TCL?
What data types exist in SQL?
What is a primary key (PRIMARY KEY)?
What is a foreign key (FOREIGN KEY)?
Tell me about normal forms (1NF, 2NF, 3NF)
What is data integrity?
What is data redundancy?
How do you create a table in SQL?
How do you drop a table?
How do you add a new column to a table?
How do you drop a column from a table?
How does DROP TABLE differ from DELETE?
What is DML in SQL?
How do you insert a record into a table?
How do you update a record in a table?
How do you delete a record in a table?
What does the TRUNCATE command do?
How do you insert several rows in one query?
What happens if you don't specify all required fields in INSERT?
What is auto-increment (AUTO_INCREMENT / SERIAL)?
How do you make a field unique in a row?
How do you delete all rows from a table?
What does ON DELETE CASCADE do?
What does the MERGE command do?
What does the SELECT command do in SQL?
How do you select all columns of a table?
How do you select only specific columns?
How do you select unique rows from a table?
What does DISTINCT do?
What does GROUP BY do?
What does LIMIT do in SQL?
How do you return only the first 10 records?
Where can subqueries be used?
How do you filter rows by condition?
What does the WHERE operator do?
What does LIKE do?
What does the BETWEEN operator do?
How do you set several filter conditions at once?
What does the IN operator do?
What does NOT IN do?
How do you work with logical operator precedence?
What does ORDER BY do?
How do you sort data in ascending order?
How do you sort data in descending order?
What do ASC and DESC do?
How do you sort by multiple fields?
What do NULLS FIRST and NULLS LAST do?
How do you combine ORDER BY and LIMIT?
Why do you need to combine tables?
How does JOIN differ from a subquery?
Can you join more than two tables?
What are relationships between tables?
Tell me about a 1:1 (one-to-one) relationship
Tell me about a 1:many (one-to-many) relationship
Tell me about a many:many relationship
What does LEFT JOIN do?
What does RIGHT JOIN do?
What does FULL OUTER JOIN do?
What does CROSS JOIN do?
What is a cartesian product?
What does USING do in a JOIN?
What is data aggregation in SQL?
What does the COUNT() aggregate function do?
What does SUM() do?
What do MIN() and MAX() do?
What does GROUP BY do?
How does grouping work in SQL?
How are aggregate functions related to GROUP BY?
How do you group data by a single field?
How do you group data by multiple fields?
What does HAVING do? How does HAVING differ from WHERE?
What is an index in SQL? Why do we need indexes?
How does an index speed up data lookup?
How does an index affect insert and update speed?
What does the term "index tree" mean?
What is a clustered index (clustered index)?
What is a non-clustered index (non-clustered index)?
What is a covering index (covering index)?
What is a composite index?
Why aren't indexes always useful?
How are indexes implemented inside a DBMS?
What is a B-Tree index?
When are Hash indexes more effective?
How do you create an index in SQL?
What is a "functional index"?
What is a transaction in SQL?
Why do we need transactions?
What does the term "atomicity" mean?
Why are transactions important for data integrity?
What is ACID?
What does "Consistency" mean in ACID?
What does "Isolation" mean in ACID?
What does "Durability" mean in ACID?
What happens if a transaction fails midway?
How do you start a transaction in SQL?
What does the COMMIT command do?
What does the ROLLBACK command do?
Why do transactions guarantee atomicity?
How do transactions ensure data consistency?
What is a transaction isolation level?
What is a lock in SQL?
What is a view (VIEW) in SQL?
Why do we need views?
How do you create a view?
Can you insert data into a view?
Can you update data through a view?
Can you delete data through a view?
How do views affect performance?
What is a function in SQL?
How do you create a function?
What is a deterministic function?
What is a non-deterministic function?
What is a trigger in SQL?
Why do we need triggers?
What types of triggers exist?
What does a row-level trigger do?
What are the pros and cons of using triggers?
What does database administration include?
What does the term "instance" mean for a database?
What is a "schema" in SQL?
How do clients connect to a database server?
What are "configuration files" in a DBMS?
Why do we need an undo / rollback log?
What is a user in SQL?
How do you create a user?
What are access privileges (privileges)?
What types of backups exist?
How often should you back up?
Why do we need database monitoring?
What metrics matter when administering a database?
What does "SQL injection" mean?
How do you protect against SQL injections?
What is database scaling?
How does scaling differ from optimization?
What is a "bottleneck" in a database?
What types of scaling exist?
What is horizontal scaling (horizontal scaling)?
Why is it important to separate read and write load?
What is PgBouncer and why do you need it?
What is replication in SQL?
How does replication help scale a database?
What does "master-replica" architecture mean?
How does synchronous replication differ from asynchronous replication?
What is partitioning (partitioning)?
What is sharding (sharding)?
How does partitioning differ from sharding?
What sharding strategies exist?
What is load balancing (load balancing)?
How do you distribute requests across multiple replicas?
How does scaling affect data consistency?
What is a database cluster?
MongoDB interview questions
What is MongoDB?
What does "NoSQL" mean?
How does MongoDB differ from relational databases?
Why is MongoDB called a document-oriented database?
What is MongoDB's architecture made of?
What is BSON?
Why does MongoDB store data in the BSON format?
What data types does BSON support?
Why is MongoDB considered flexible in its schema?
What is a document in MongoDB?
What is a collection in MongoDB?
What is a database in MongoDB?
What does a BSON document example look like?
What is ObjectId?
How does a collection differ from a SQL table?
What is a nested document (embedded document)?
What is a dynamic data schema?
What is a schema in MongoDB?
How do you create several documents at once?
How do you update a document in the DB?
How do you delete a document in the DB?
How does replaceOne() differ from updateOne()?
What does "atomicity" mean in the context of CRUD?
How do you find a document in the DB?
What does limit() do?
What does skip() do?
How do you sort the result?
What are bulk operations in MongoDB?
Which method takes the filter in MongoDB?
Can you filter by nested fields?
What format are filters defined in in MongoDB?
How does $eq differ from plain { field: value }?
What does $ne do?
What does $gt do?
What does $lt do?
What does $and do?
What does $or do?
What does $not do?
How do you filter documents where an array contains a specific value?
When do you need to use $elemMatch?
What does $expr do? When is $expr needed instead of standard filters?
Why are indexes needed?
How do indexes speed up search?
What does "B-tree index structure" mean?
Why do indexes slow down write operations?
What index is created automatically in MongoDB?
What is aggregation in MongoDB?
What does "aggregation pipeline" mean?
What does a stage mean in aggregation?
What does the $group stage do?
What does the $project stage do?
What does the $sort stage do?
What does the $limit stage do?
What does the $skip stage do?
What does the term "scaling" mean in the context of MongoDB?
What scaling types does MongoDB support?
How does vertical scaling differ from horizontal scaling?
What is sharding in MongoDB?
Why does MongoDB scale horizontally?
What advantages does distributed data storage give?
What is a Replica Set?
What does the primary node do?
What do secondary nodes do?
How does sharding differ from replication?
What is a shard?
What is a shard key (the sharding key)?
What is a "chunk" in MongoDB?
What is a transaction in MongoDB?
What does atomicity mean?
What does consistency mean?
What does isolation mean?
What does durability mean?
How does MongoDB implement atomicity without transactions?
Redis interview questions
What is Redis?
Why is Redis called an in-memory database?
Where does Redis store data by default?
What are the most common Redis use cases?
Why is Redis considered very fast?
What makes Redis a single-threaded system?
Why is Redis often used as a cache layer?
How does Redis use memory?
How is Redis used in task queues (Celery, Bull, RQ)?
What main data types does Redis support?
How does Redis store a value's type under the hood?
Why does Redis say "key → data structure" instead of just "key → value"?
What is String in Redis?
What is List in Redis?
What is Set in Redis?
What is Sorted Set (ZSet)?
What is Hash in Redis?
What is HyperLogLog?
What is Bitmap?
What are Geospatial types in Redis?
Why is Redis an in-memory DB?
What does the "key-value" model mean in the context of Redis?
Why is Redis faster than traditional databases?
Why is Redis considered a single-threaded system?
What does the event loop do in Redis?
Why doesn't Redis need a traditional multi-threaded approach?
How does Redis manage memory? How does Redis allocate memory for keys and values?
What is an "allocator" in the context of Redis?
What is a database index in Redis?
What is replication in Redis? Why is replication needed?
What does the "master-replica" model mean in Redis?
How do you tell whether a Redis node is a master or a replica?
How does cascading replication work in Redis?
What are the advantages of asynchronous replication?
How does replication affect performance?
How does Sentinel differ from Redis Cluster?
How does Sentinel provide Redis's fault tolerance?
What does the Sentinel system consist of?
How many Sentinel instances are recommended at minimum?
What is Redis Cluster?
How does Redis Cluster scale horizontally?
What does Redis Cluster consist of?
How are slots distributed among nodes?
What does a replica do in a cluster?
Manual Testing interview questions
Test Automation interview questions
HR Questions interview questions
Tell us about your experience
Most interesting task
The most interesting task you have worked on
Your level
Why did you choose this stack or direction
Your stack or direction
Why are you changing jobs
Changing jobs
What kind of tasks do you enjoy most
What tasks do you like
What motivates you at work
Motivation at work
The ideal team
Your ideal team or project format
Where do you see yourself in two or three years
How do you usually build up your skills?
How do you keep your skills sharp
Working here specifically
Why do you want to work here specifically
Mortgage
Overtime
Are you ready for overtime and weekend work
Why exactly you?
IT Processes interview questions
What is SDLC and why is it needed? What are the main stages SDLC includes?
Who is responsible for requirements gathering in a project?
What is a use case?
What does the design phase include?
Who is involved in architecture design?
What is an architecture diagram?
What are UML diagrams?
What is a Design Review?
Name the 4 key values of the Agile Manifesto.
How does Agile differ from Waterfall?
What is iterative development?
How does Scrum differ from Kanban?
What roles exist in Scrum?
What events does Scrum include?
What is a Product Backlog?
What is Definition of Done (DoD)?
What is a Sprint Goal?
What is a Daily Scrum and what is its goal?
What happens at a Sprint Review?
What is Sprint Retrospective?
What are the responsibilities of a Product Owner?
What are Story Points and why are they needed?
What is a user story?
What is velocity and how is it used?
How is team progress measured?
What are lead time and cycle time?
How to evaluate the performance of a Scrum team?
What is a cumulative flow diagram?
Why are predictability metrics needed?
What is Kanban?
How does Kanban differ from Scrum?
What is a Kanban board?
How does Kanban help identify bottlenecks in a process?
What does continuous flow mean?
List the main principles of Kanban.
How do Kanban principles improve transparency?
Why is it important to have a "Definition of Done"?
What is WIP in Kanban? Why is it important to limit the number of tasks in progress?
How do you measure flow speed?
What does "bottleneck" mean?
How to identify a bottleneck in the flow?
What does "cumulative flow diagram" mean?
What metrics are used in Kanban?
What does "lead time" mean?
What does "cycle time" mean?
What does the term "functional team" mean?
What does the term "cross-functional team" mean?
What daily or weekly meetings are most common in IT teams?
What does a team lead do?
What is the difference between a Product Owner and a Project Manager?
How do developers and QA interact during testing?
What ways of sharing knowledge exist within a team, and why does it matter?
How does code review work?
Can you do without code review?
How do feature flags help test new features?
Why is planning needed in the development process?
What is a version control system?
What is the Git Flow approach to development?
What is a feature branch?
What does "pull request" mean?
What is the purpose of code review?
What does Continuous Integration (CI) mean?
Why is CI important for release stability?
What does a typical CI pipeline include?
How does CI integrate with Docker?
Who is responsible for a release?
What is a release cycle?
What is A/B testing?
What is a feature flag?
Describe the release process on your team.
How do you resolve branch merge conflicts before a release?
Questions To Ask interview questions
The product
Problem
Stage of development
Current Development
Existence
Team Size
Team type
Code Review
Meetings
TS
Methodology
Processes
Onboarding
Documentation
Performance Review
Branching model
Technology Stack
Legacy
Project architecture
Infrastructure
Releases
On-call
Tech debt
Bugs
Tests
Grades
Performance Review
Getting started
Growth
Work format
Work Schedule
Communication tools
Calls
Business trips
Bonuses
Promotion
Probation period
General Questions interview questions
How to debug application and find memory leaks
What is critical rendering path (crp) in browser
CSR, SSR, SSG, ISR — difference between rendering strategies
What is the difference between functions and procedures in SQL?
When reflow and repaint occur in browser
What are composite indexes?
ACID - atomicity
How browser works when entering request and rendering stages
What is service worker?
What is three-way handshake?
Server-sent events, polling and long polling: what they are and when to use
Modern browser architecture (processes and threads)
Browser storage: cookie, LocalStorage, SessionStorage and IndexedDB
Resource loading strategies - preload, prefetch, modulepreload
What are symmetric and asymmetric keys in encryption?
How HTTP works and what an HTTP request consists of
HTTP status codes
How HTTPS works and difference from HTTP
HTTP/2 vs HTTP/3: protocol evolution
What is REST and REST principles — REST API
What is the difference between PUT and PATCH?
Can you send a body in a GET request?
Parsing pipeline - from bytes to DOM and CSSOM
What is shadow DOM in web development
Immutability and mutability in JavaScript
V8 architecture: from code to machine instructions
What is the difference between process and thread in Node.js?
What is progressive rendering in web development
What is the difference between authorization and authentication?
What is JWT and how does it work?
What is CORS and how does it work?
What is XSS and how to prevent it?
What is CSRF and how to prevent it?
How does left join work?
How does right join work?
What are referential actions in SQL?
What are clustered and non-clustered indexes?
What is Webpack?
Types of frontend testing
What is CDN and why is it needed?
What is throttling?
What are noisy tenants?
