Hi! Personally I’d keep the Onboarding a single deployable unit until it makes sense to break it down into smaller services.

Domain-driven-design will give one the tactical tools to structure a monolith without all the headaches of actually doing microservices. If it needs to be broken down into smaller deployable units then the code base will already be structurally ‘microservice-ready’.

In that process, looking for volatility will reduce the pain. Looking at Onboarding — what are the most stable and fundamental checks (or group of checks), and conversely what are the most immature, unstable and uncertain parts of the design? The strategic tools from DDD will also help here.

Those are my initial thoughts.