Definition
An API Gateway is a server that acts as a single entry point for clients accessing various backend services. It handles incoming requests, routes them to the appropriate microservice or application, and then returns the response to the client. This abstraction simplifies client interactions and allows backend services to evolve independently without affecting consumers. API Gateways often manage tasks like authentication, authorization, rate limiting, and request transformation, centralizing cross-cutting concerns. For instance, a mobile app might use an API Gateway to access user profiles, order processing, and payment services, all through one unified interface. Unlike a simple load balancer that distributes traffic, an API Gateway provides intelligent routing and policy enforcement. This concept is fundamental in cloud architecture and frequently appears on exams like AWS Certified Solutions Architect and CCSP.