API Gateway Pattern

Microservices spread functionality across many internal services, but external clients should not need to know that structure.

An API Gateway provides one stable entry point for web apps, mobile apps, and partner integrations. It handles common edge concerns like authentication, rate limiting, routing, and TLS, then forwards requests to the right internal service.

This chapter covers direct service exposure, gateway responsibilities, edge authentication, rate limiting, response aggregation, and why gateways should handle cross-cutting concerns, not business logic.