An API gateway is a server or managed service that acts as a central entry point for client requests to backend APIs and services. Instead of clients communicating directly with multiple internal services, the gateway receives requests, determines where they should go, and can apply common policies before forwarding them. It can also handle authentication, authorization, rate limiting, request routing, protocol translation, and response aggregation.
In a microservices architecture, an API gateway can shield internal services from direct external access while providing a consistent interface for applications. For example, a mobile application may send one request to the gateway, which retrieves information from several backend services and returns a combined response. This reduces client-side complexity and centralizes API traffic management.
