What is caching, and how can it be implemented in REST APIs?

Short answer: Caching is storing frequently used data temporarily to reduce server load and improve response time. Implementation methods: HTTP caching headers (Cache-Control, ETag, Expires). Reverse proxies (Varnish, NGINX). In-memory stores (Redis, Memcached). Client-side caching using 304 Not Modified.

Real-world example (ShopNest)

Creating an order is POST /api/orders → 201 with Location header. Fetching is GET /api/orders/{id} → 200 or 404.

Say this in the interview

1. Define — one clear sentence (the short answer above).
2. Example — relate it to a project like ShopNest or your real work.
3. Trade-off — when you would not use it.