An API gateway serves as the single entry point for client requests in microservices and distributed architectures, managing routing, security, rate limiting, and protocol translation between clients and backend services. This centralized control plane enables consistent policy enforcement across all APIs while decoupling client interfaces from backend implementations. Key to modern cloud-native applications, effective gateway configuration balances security, performance, and developer experience — implementing patterns like request transformation, circuit breaking, and canary deployments ensures resilience while maintaining sub-100ms latency for critical traffic paths.