General Questions
Cross-cutting topics: HTTP, the browser, security, rendering, databases and testing.
How data travels across the internet: setting up a TCP connection, the anatomy of an HTTP request, response codes, encrypted transport and newer protocol versions.
Designing REST interfaces, the semantics of HTTP methods, and the ways a client receives real-time updates from a server.
What happens between typing a URL and seeing pixels on screen: browser processes, parsing markup and styles, the critical rendering path, reflow and repaint.
Where an app keeps data on the client side, and which browser APIs provide style isolation, background computation and offline behaviour.
How code is turned into machine instructions, how the engine treats values in memory, and how a process differs from a thread.
Choosing between client-side, server-side and pre-built pages, plus the techniques that speed up loading and interface responsiveness.
Confirming who a user is and what they may do, working with keys and tokens, and defending against the most common web attacks.
Joining tables in queries, indexes and their effect on speed, data integrity rules and the ACID transaction guarantees.
Bundling a project, the levels of automated testing, and tracking down bugs and memory leaks in an application.
Delivering content through CDN networks, limiting the load a service accepts, and the noisy-neighbour problem in shared infrastructure.