API gateway

A single entry point in front of backend services that handles routing, authentication, rate limits and TLS for all of them.

Clients talk to one address; the gateway checks the token, applies rate limits and forwards the request to the right service. It keeps those concerns out of each service and gives one place for logs and metrics. The risks are a single point of failure and a slow drift of business logic into gateway configuration, where nobody tests it.

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Related terms

BFF (backend for frontend): A small backend built for one client, such as the web app or the mobile app, that shapes data exactly the way that client needs it.
Rate limiting: Capping how many requests a user, key or IP can make in a time window, and answering HTTP 429 above it.
Circuit breaker: A guard around calls to a dependency that stops calling it after repeated failures and fails fast until it recovers.

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