Synchronous communication

Synchronous and asynchronous communication are two approaches to interaction in software design.

Synchronous communication is when sender and receiver components interact in real-time. This is the default mode of interaction for most components within a monolithic software system. In most programming languages, function calls are synchronous by default, meaning that the caller waits for the callee to return a value before it proceeds further with its own execution.

Synchronous communication is more commonly discussed in the context of distributed software, where it is implemented using request-response communication protocols such as HTTP or gRPC.

Synchronous communication in distributed software requires individual services within the network to expose their own [APIs], rather than relying on a [message broker], [event bus], or other intermediary system to manage communication between services.

Synchronous communication in distributed software can lead to tight coupling between services, making it difficult to change services independently of each other. However, it is often necessary when low [latency] or [real-time data] processing is a requirement, or when data consistency is a primary [constraint].

It is best practice for services that depend on synchronous communication to serve a [health check] endpoint. This allows clients to check the availability of the services on which they depend. Alternatively, load balancers can monitor the health check endpoints and route traffic to healthy services.