Explain advanced API Gateway architecture and request orchestration in large-scale PHP systems.

API Gateways centralize routing, authentication, rate limiting, transformation, and orchestration for distributed PHP microservices.

An API Gateway is the single entry point for client requests in a distributed system. At scale, it evolves from a simple reverse proxy into a distributed control plane for APIs.

Core responsibilities:

Maps incoming requests to backend services.

Validates JWT, OAuth2 tokens, API keys.

Prevents abuse and ensures fairness.

Adapts payload formats per client.

Combines multiple microservice responses into a single response.

6.…