Software Architect's Handbook

Synchronous request

When a client makes a synchronous request, it waits for a response. A request-reply pattern is used to handle synchronous requests. Examples of requests include an HTTP request or a gRPC call. The following diagram shows the flow of a synchronous request, which first goes through an API gateway:

In order to locate a function instance, the API gateway will either use client-side service discovery or pass it on to a router (load balancer) for server-side service discovery. Once a service instance is located, the request is passed to it for processing. Once execution of the function is complete, the response is sent back ...