API Gateways and Service Discovery

Once you have a dozen services, two problems appear. Clients shouldn't need to know each service's address or call five of them to render one screen — that's the API gateway's job. And services that scale up/down and move IPs need a way to find each other — that's service discovery.

This lesson covers both, with PHP at the gateway edge.

An API gateway is a single entry point in front of your services. Typical responsibilities:

• Routing requests to the right backend.
• Cross-cutting concerns: authentication, rate limiting, CORS, TLS termination.
• Aggregation: compose several backend calls into one client response.
• Protocol translation: external REST in, internal gRPC out.

It keeps clients simple and centralizes policy you'd otherwise duplicate in every service.