What an API Gateway Actually Does Beyond Just Routing Requests

An API gateway is a centralized layer that sits in front of all backend services, giving clients a single endpoint while handling routing internally. As systems grow to include multiple services and client applications, concerns like authentication, rate limiting, versioning, and tracing must be managed consistently across all of them. Without a gateway, each service tends to implement its own version of this shared logic, leading to inconsistencies that can introduce security vulnerabilities. Unlike a load balancer, which distributes traffic among identical replicas of one service, an API gateway routes requests across different services and enforces application-level policies before forwarding them. In practice, both components work together, with a load balancer spreading traffic across gateway instances and the gateway handling service-aware routing and policy enforcement downstream.