What is an API Gateway and how does Spring Cloud Gateway work? API गेटवे क्या है और स्प्रिंग क्लाउड गेटवे कैसे काम करता है?

An API Gateway is a single entry point that sits in front of all microservices, routing incoming requests to the correct downstream service and centralizing cross-cutting concerns like authentication, rate limiting, request/response logging, and CORS, so individual services don't need to reimplement them.

Spring Cloud Gateway, built on Project Reactor for non-blocking, reactive routing, matches requests to routes based on predicates (path, header, method) and applies filters (add headers, rewrite paths, apply a circuit breaker) before forwarding the request, often resolving the destination service dynamically through Eureka rather than a hardcoded URL.

spring:
  cloud:
    gateway:
      routes:
        - id: order-service
          uri: lb://ORDER-SERVICE
          predicates:
            - Path=/api/orders/**
          filters:
            - StripPrefix=1