Over the last few months I've been working on Differential.dev.

It's a tool that I built to solve the problem of connecting n domain services, with the simplest possible abstraction - function calls. (Typescript only for now)

Internally it uses a service bus that ferries functions calls, but all of this is abstracted away from a developer. You can use it (as I have) in brown-field projects to split a monolithic service to domain-driven services, without splitting the codebase.

It's fully open-source under a GPL 3.0 License: https://github.com/differentialHQ/differential

Keen for feedback, if you have any. You can also contact me at nadeesha at differential.dev.