Networking

Async JS: API fetch with a timeout

CORS, preflight requests, and SameSite cookies

Difference between fetch and axios

How do you fetch data in Next.js using getStaticProps and getServerSideProps

Cache-Control directs *how long* responses are cached. ETag/Last-Modified enable *revalidation* — client sends If-None-Match, server returns 304 if unchanged. Combine: long max-age for hashed assets, short max-age + revalidation for HTML/API.

If a user clicks a button multiple times to fetch data, how to cancel old API calls and use only the latest result

Implement fetch with a timeout/abort feature

WebSockets vs HTTP — and why aggressive polling is a bad idea

Polling is simplest (HTTP). SSE is one-way server→client (text, auto-reconnect, HTTP/2-friendly). WebSockets are bidirectional, binary-capable, lowest-latency. Pick the *least* powerful that fits — operational cost rises with each.

What is CORS and how does it work

What is RTK query ? How is it different from axios & fetch.

What is the use of Headers in HTTP requests