API Gateway

The API gateway is the front door to your microservices. Understand it as a solution to the 'cross-cutting concerns' problem — without a gateway, every service would need to implement auth, rate limiting, logging independently. The gateway centralizes these concerns. What is an API Gateway? An API Gateway is a single entry point for all client requests to your backend services. Instead of clients calling 10 different microservices directly, they call one gateway that routes requests to the right service. Why Not Let Clients Call Services Directly? Security: Clients shouldn't know internal service locations Complexity: Client would need to track 10service URLs Cross-cutting concerns: Auth, rate limiting, logging — done once at the gateway instead of in every service Protocol translation: Gateway can accept REST and convert to gRPC internally Real-World Examples Netflix Zuul/Spring Cloud Gateway: Handles billions of requests/day Amazon API Gateway: Managed service, scales automatically Kong: Open-source, plugin-based, built on Nginx Interview Tip 'An API Gateway is essential in microservices architecture. It handles cross-cutting concerns like authentication, rate limiting, and request routing in one place, instead of duplicating that logic across every service.' Python Implementation Java Implementation JavaScript/TypeScript Implementation