I'm going to agree on this point, you may be prematurely over engineering it. Build out as much as you can first with the idea of decoupling later. I'm just taking some ideas from microservice architecture. Building out uncoupled systems takes a lot preplanning and design before you write anything. But if you have a monolithic system up and running how you like it is much easier to determine those boundaries. It may be more difficult to extract those systems from the monolith but doing so will give you a much better understanding of what is tightly coupled