I think this is a great recommendation for any new project that is considering to use Microservices. I like the approach of an in-memory event-driven system. This helps to enforce a message-only relationship between different conceptual parts from the start.

In fact, I did the same in one project. Also, while I am not covering Microservices in my book, the Sample Application uses a similar approach. The different contexts integrate via event communication. At first, this is an in-memory implementation and everything is running in a single process. Later on, it is replaced with a filesystem-based variant and the individual contexts are operated as individual programs.