APIGateways

An API gateway is a server that serves as the single entry point for a collection of backend services. It handles incoming client requests, routes them to the appropriate microservice or backend, and returns the aggregated response to the client. API gateways are commonly employed in microservices architectures to shield clients from the complexity and topology of multiple services, enabling centralized control over traffic and policies.

Core functions typically provided by an API gateway include request routing, protocol translation, and request/response transformation. They also enforce security policies such as authentication and authorization, support rate limiting and quota management, implement caching and load balancing, and handle retries and circuit breaking. Observability features like centralized logging, metrics, and distributed tracing are often integrated to monitor performance and troubleshoot issues. Gateways may also perform API versioning, request aggregation or composition, and response shaping to optimize payloads for clients.

APIs gateways come in different deployment models. Cloud-managed gateways are offered as a service by cloud providers; self-hosted gateways run on customer infrastructure. They can operate at the edge (facing clients) or internally within a data center or cloud network. Some gateways are primarily reverse proxies with gateway features, while others are part of broader API management platforms that include developer portals, analytics, monetization, and policy governance.

In practice, an API gateway complements other architectural patterns such as service meshes. While a gateway handles north-south traffic and centralized policies, a service mesh manages east-west traffic between services. Together, they provide layered control over API access, reliability, and security.