> Then you have a schema layer that could change in backwards compatible ways. Every new addition is optional.

Also known as the rest of the fucking owl. I am entirely in factual agreement with you, but the number of people who are even aware they maintain an API surface with backwards compatibility as a goal, let alone can actually do it well, are tiny in practice. Especially for internal services, where nobody will even notice violations until it’s urgent, and at such a time, your definitions won’t save you from blame. Maybe it should, though. The best way to stop a bad idea is to follow it rigorously and see where it leads.

I’m very much a skeptic of microservices, because of this added responsibility. Only when the cost of that extra maintenance is outweighed by overwhelming benefits elsewhere, would I consider it. For the same reason I wouldn’t want a toilet with a seatbelt.