The microservices architectural pattern is a popular pattern. Software architects and developers use it to divide a system into distributed, loosely coupled services. Services should perform independently of each other so that they can be implemented, maintained and deployed independently, even by different teams.

Microservices use communication protocols to coordinate the work they do for the system as a whole. Whenever multiple services are involved in implementing a feature of the system, careful planning of the distributed operations is required to avoid communication loops or deadlocks.

This paper presents an industrial case study and examines the challenges faced by software architects and developers in planning the orchestration and assessing the correctness of event-driven communication behaviour.

Despite the simplicity of the microservices pattern, architects and developers report a high level of complexity tracing the communication between the individual services. They find it challenging to document the message paths across all services, and therefore have to reconstruct them from source code every time they plan changes to the system.

We present a novel approach to visualize the communication paths of an event-driven microservice system. Service-local documentation is used to create a global view of the runtime behaviour. We show that this visualization approach can significantly reduce the time required to understand an architecture, while additionally improving accuracy and confidence.