> But, unless you have some way of enforcing that access between different components happens through some kind of well defined interfaces, the codebase may end up very tightly coupled and expensive or impractical to evolve and change
You are describing the "microservice architecture" that I currently loathe at my day job. Fans of microservices would accurately say "well that's not proper microservices; that's a distributed monolith" but my point is that choosing microservices does not enforce any kind of architectural quality at all. It just means that all of your mistakes are now eternally enshrined thanks to Hyrum's Law, rather than being private/unpublished functions that are easy to refactor using "Find All References" and unit tests.
You are describing the "microservice architecture" that I currently loathe at my day job. Fans of microservices would accurately say "well that's not proper microservices; that's a distributed monolith" but my point is that choosing microservices does not enforce any kind of architectural quality at all. It just means that all of your mistakes are now eternally enshrined thanks to Hyrum's Law, rather than being private/unpublished functions that are easy to refactor using "Find All References" and unit tests.