What is the difference between PUT and PATCH in REST APIs?

Short answer: PUT: Replaces the entire resource with the data sent. If a field is missing in the request, it may get erased. Idempotent (same request repeated yields same result). PATCH: Applies partial updates to the resource. Only changes the fields specified. Not necessarily idempotent.

Example code

Updating user email. PUT /users/1 with { "name": "Alice" } replaces whole user — email might get removed. PATCH /users/1 with { "email": "new@example.com" } updates just the email.

Real-world example (ShopNest)

A ShopNest BFF in Node.js aggregates catalog and price APIs for the React storefront.

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.