The API gateway is the single entry point for all client traffic. It handles routing to downstream services, authentication, rate limiting, and request/response transformation — so individual services don’t have to. Setup <dependency> <groupId>org.springframework.cloud</groupId> <artifactId>spring-cloud-starter-gateway</artifactId> </dependency> <dependency> <groupId>org.springframework.cloud</groupId> <artifactId>spring-cloud-starter-netflix-eureka-client</artifactId> </dependency> Spring Cloud Gateway is reactive (WebFlux-based) — don’t include spring-boot-starter-web. Route Configuration YAML Configuration spring: application: name: api-gateway cloud: gateway: routes: - id: order-service uri: lb://order-service # lb:// = load-balanced via Eureka predicates: - Path=/api/orders/** filters: - StripPrefix=0 # don't strip path prefix - AddRequestHeader=X-Gateway-Source, api-gateway - id: customer-service uri: lb://customer-service predicates: - Path=/api/customers/** filters: - StripPrefix=0 - id: payment-service uri: lb://payment-service predicates: - Path=/api/payments/** filters: - StripPrefix=0 # Versioned routing - id: order-service-v2 uri: lb://order-service-v2 predicates: - Path=/api/v2/orders/** - Header=X-API-Version, 2 default-filters: - DedupeResponseHeader=Access-Control-Allow-Credentials Access-Control-Allow-Origin Programmatic Route Configuration @Configuration public class GatewayRouteConfig { @Bean public RouteLocator routeLocator(RouteLocatorBuilder builder) { return builder.

Building microservices requires more than splitting a monolith into services. You need service discovery, a gateway to route traffic, centralised configuration management, and resilience patterns to handle inevitable failures. Spring Cloud provides all of this as a cohesive stack. This guide builds a complete microservices architecture from scratch: Eureka for service discovery, Spring Cloud Gateway for routing, Spring Cloud Config Server for centralised config, and Resilience4j for circuit breakers and retry.