Learn vocabulary for API gateway roles, BFF pattern, rate limiting, gateway aggregation, and sidecar pattern in microservices.
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What is the primary role of an API gateway in a microservices architecture?
An API gateway is the front door to your microservices system. Clients call the gateway; the gateway routes requests to the appropriate downstream services. It centralizes cross-cutting concerns: authentication/authorization, rate limiting, SSL termination, request/response transformation, logging, and tracing — so each service doesn't re-implement them.
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What is the Backend for Frontend (BFF) pattern in API gateway vocabulary?
BFF (Sam Newman): instead of one general-purpose API gateway, create one gateway per frontend type. The mobile BFF returns compact payloads optimized for mobile bandwidth; the web BFF returns richer data. Each BFF is owned by the team building that frontend. This avoids the 'general-purpose gateway' anti-pattern where one gateway tries to serve conflicting client needs.
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What is 'rate limiting at the gateway' in microservices vocabulary?
Rate limiting at the gateway enforces request quotas: e.g., 1000 requests per minute per API key. When the limit is exceeded, the gateway returns 429 Too Many Requests without forwarding to downstream services. This protects backend services from overload, prevents abuse, and enables fair usage policies — all in one centralized place.
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What is 'gateway aggregation' in microservices vocabulary?
Gateway aggregation (also called API composition): the client makes one request to the gateway; the gateway calls Service A, Service B, and Service C in parallel, combines their responses, and returns a single response. This reduces client complexity and network round trips — especially valuable for mobile clients with high latency or limited connections.
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What distinguishes the sidecar pattern from an API gateway in microservices vocabulary?
Sidecar pattern (used in service meshes like Istio/Linkerd): a proxy container runs next to each service instance, intercepting all inbound and outbound traffic. It handles mTLS, retries, circuit breaking, and telemetry — transparently, without changing service code. An API gateway handles north-south traffic (client→system); sidecars handle east-west traffic (service→service).