On a number of occasions we have seen system designs that use request-response events in user-facing workflows. In these cases, the UI is blocked or the user has to wait for a new page to load until a corresponding response message to a request message is received. The main reasons cited for designs like this are performance or a unified approach to communication between backends for synchronous and asynchronous use cases. We feel that the increased complexity—in development, testing and operations—far outweighs the benefit of having a unified approach, and we strongly suggest to use synchronous HTTP requests when synchronous communication between backend services is needed. When implemented well, communication using HTTP rarely is a bottleneck in a distributed system.
