API Gateway

An API gateway is the front door of a modern application's backend. Every request from clients — web browsers, mobile apps, third-party services — passes through the gateway, which routes it to the appropriate microservice. Along the way, the gateway handles cross-cutting concerns like authentication, rate limiting, request transformation, caching, and monitoring, so individual services do not have to.

Popular API gateways include Kong, AWS API Gateway, Nginx, and Traefik. In simpler architectures, frameworks like Next.js API routes or Express middleware serve similar functions. The key benefit is centralization: instead of implementing authentication in every service, you implement it once at the gateway. Instead of monitoring each service individually, the gateway provides a unified view of all API traffic.

For AI-powered applications, API gateways take on additional responsibilities. They can route requests to different AI models based on complexity, manage token budgets across services, enforce usage quotas, and provide a unified interface even when the underlying AI infrastructure changes. At Agentik {OS}, our API architecture uses gateway patterns to manage communication between agents, external services, and client applications — ensuring reliable, secure, and observable interactions across the entire system.