Documenting the aggregates & relations between microservices

Question

In my organization we're trying to design our microservices based on the Bounded Context (BC) pattern (part of Domain-driven design). While we're doing this we also try to use another DDD pattern called the Context Mapping, to better identify the various contexts in the application, their boundaries and the relations between them.

All of this can be done on a whiteboard or in some online drawing tool. However, I'm looking for a way to generate a complete picture of the various services, what aggregates they contain and potentially the relations between such aggregates (as the same User in one BC might be a Customer in another). A good example is figure 4-10 in here. The generation should ideally be based on some DSL or script which we would maintain, as this kind of work is fairly high-level and context boundaries don't change very often. For example, a team adds a new aggregate or starts keeping a copy of an aggregate from another service, they update the script/DSL and regenerate the diagram.

Solutions I've looked at so far:

• Context mapper - it doesn't visualise the aggregates in each BC/service, nor does it show relations
• C4 model, Level 2 - we already use it, so it could be fairly easy to add a textual list of aggregates per container, but it's not what it's intended for (and the visualisation is not optimal)
• ddd bounded context/microservice canvas - it's too detailed and can't really be used to look at the big picture

I'm wondering how and if this is done in other organization, and looking for suggestions for some tooling that would be of help.

Answer 1

I think the format used for event storming sessions might be worth to have look at in your case. Once done it covers all domain events, commands, actors, read models, policies, external systems. Also it illustrates the bounded contexts in which the aggregates, events, etc. live in. An example can be found here: https://medium.com/capital-one-tech/event-storming-decomposing-the-monolith-to-kick-start-your-microservice-architecture-acb8695a6e61

I know the format is mainly used for domain exploration but from my experience, if done nicely (e.g. using some tool like Miro, Lucid, or the like) it also provides good documentation and overview of what's going on in your system.