API Gateways

An API gateway is an infrastructure component that sits between clients and backend services, handling cross-cutting concerns like authentication, rate limiting, routing, and protocol translation in one place rather than repeating them in every service.

itDistributed systems, messaging, and integration

Don't Panic — API Gateways

An API gateway is the front desk for an API. Clients call one address, and the gateway chooses the backend and boundary rules. Backends can move, split, or live on private addresses without every client receiving a new map and a tiny compass.

The gateway is on the request path. It accepts a connection, matches a route, applies policy, calls a backend, and returns a response. Routing is the core job. TLS handling, credential checks, traffic limits, transformations, caching, and telemetry are additions. Each changes request behavior, so each needs a test and a rollback plan.

The management plane defines routes, policies, credentials, and deployments. The data plane handles live requests. Existing traffic may need to continue while configuration changes are unavailable. A bad configuration needs to reach the data plane slowly enough that it can be stopped.

A gateway is not a promotion ceremony for every concern in a system. It can validate a token and apply a coarse scope. The backend still decides whether that caller may use a specific object or function. Aggregation can reduce client round trips while quietly adding dependencies, which is the architectural equivalent of putting groceries on one very confident bicycle.

HTTP keeps its rules after the gateway arrives. Preserve method intent, status codes, cache directives, validators, and content negotiation unless the contract changes. Trust forwarding information only after a controlled proxy adds it. Rate limits protect capacity, but do not create it.

Read the intro for the request path and limits. Use slides to compare routing, offloading, and aggregation. Keep the cheatsheet near when reviewing policy order, forwarding trust, failures, and rollouts. The exercise gives you a small gateway boundary to test.

Don't Panic — API Gateways

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