Rate limiting prevents abuse and ensures fair use. Implement at the app (e.g. middleware) or edge (WAF, nginx). Use per-IP or per-key limits; return 429 and Retry-After. Tier-III networks often add DDoS protection upstream.
Why rate limit
- Abuse: Bots and scrapers can overload your API or consume quota. Rate limits cap how much one client can do.
- Fair use: Ensures one heavy user does not starve others. Per-user or per-key limits support quota and tiers.
- Cost and stability: Reduces surprise traffic spikes and helps you size and budget capacity.
Where to implement
- Application: Middleware or decorator that checks request count per key/IP and returns 429 when over limit. Full control; can use Redis for distributed limits.
- Edge: Nginx limit_req, WAF, or API gateway. Offloads work from the app; consistent across all endpoints. Combine with app-level for per-user/key limits.
- Provider: Some hosts offer DDoS mitigation and basic rate limiting at the network edge. Complements app/edge limits.
How to implement
- Per-IP: Simple; good for anonymous or unauthenticated traffic. Can be bypassed with many IPs (botnets).
- Per API key or user: Better for authenticated APIs; ties limit to identity. Use when you have keys or sessions.
- Sliding or fixed window: Count requests in a time window; sliding is fairer but slightly more work. Return 429 Too Many Requests and Retry-After header so clients can back off.
Summary
Rate limit at app or edge; use per-IP or per-key; return 429 and Retry-After. Reduces abuse and ensures fair use; combine with provider DDoS protection for volumetric attacks.
