I have never seen a "hard boundary" in a small to medium sized company. Everyone still ends up communicating, and there are simply not enough resources to maintain truly separate services.

The rigor of maintaining resilient, backward-compatible, versioned internal APIs is too resource and time consuming to do well. All I see is hack and slash, and tons of technical debt.

It seems like in the last couple of years it started sinking in, that distributed systems are hard.