The way we handle this (we have 18 internal services) is that processes requiring transactions are formalized into a endpoint/resource. The actual transaction b

The way we handle this (we have 18 internal services) is that processes requiring transactions are formalized into a endpoint/resource. The actual transaction becomes tangible (e.g. you can cancel them by DELETE-ing on the resource) instead of just being documented. Only logic the client needs is the data to kick off the process. Async or long-running processes get a little tricker, but polling or webhook callbacks work fine for us.