A Single Front Door
In a microservice system, clients should not call dozens of services directly. An API gateway is one entry point that handles cross cutting concerns and routes each request to the right service. With aggregation, the gateway calls several services for one client request and merges their replies into a single response.
What the Gateway Handles
- Authentication, rate limiting, and TLS termination in one place.
- Routing and aggregation of multiple backend calls.
- Protocol translation, such as exposing REST over internal gRPC.
Aggregation Care
Fan out calls in parallel so total latency is the slowest call, not the sum. Decide how to handle a partial failure; often the gateway returns the data it got plus an error note for the missing piece.
Watch the Risks
A gateway can become a bottleneck or a single point of failure, so run it replicated behind a load balancer. Keep business logic out of it; the gateway routes and composes, it does not own domain rules.
Key idea
An API gateway is a single entry point that handles cross cutting concerns and aggregates parallel service calls into one response, while staying replicated and logic free.