What the gateway does
- Routing —
/users/* → User Service, /orders/* → Order Service - Authentication — token verification once, not in every service
- Rate limiting — centralised for all services
- Aggregation — one client request → multiple microservice calls → one response
- SSL termination, logging, caching
Popular solutions
Kong, AWS API Gateway, Nginx, Traefik, Envoy. Often combined with a service mesh for internal traffic.