How do you secure REST APIs (authentication, authorization)?

Short answer: Authentication → API Keys, JWT, OAuth2. Authorization → Role-based access control. Always use HTTPS. Validate input & sanitize data. Prevent SQL injection, XSS, CSRF.

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.