API Gateway Pattern — A Single Entry Point for Clients

A mobile application needs data from five microservices. Five HTTP calls, five different URLs, five authentication handshakes. An API Gateway aggregates, routes, and secures — the client communicates with a single endpoint.

What an API Gateway Solves¶

• Request routing: /api/users → user-service, /api/orders → order-service
• Authentication: JWT validation in one place
• Rate limiting: Protection against DDoS and abuse
• Response aggregation: Combining data from multiple services into a single response
• Protocol translation: REST for clients, gRPC internally
• Caching: Edge cache to reduce load on services

Implementation¶

Netflix Zuul: Java, Spring Cloud integration, battle-tested. Kong: Nginx-based, plugin architecture, Lua extensions. Nginx/OpenResty: Performant, configurable, but more work.

Backend for Frontend (BFF)¶

One gateway for all clients? Not always ideal. A mobile client needs different data than a web application. BFF pattern: a dedicated gateway for each type of client — mobile BFF, web BFF, partner BFF.

Risks¶

The API Gateway is a single point of failure. It must be highly available, fast, and resilient. It must not become a bottleneck. Keep it thin — routing and cross-cutting concerns yes, business logic no.

A Gateway is Essential for Production Microservices¶

Without an API Gateway you expose your internal architecture to clients. With a gateway you have control, security, and flexibility. A mandatory pattern for microservices.