This seems quite subjective - I have worked with services like these and would probably call that SOA where you need to split code concerns along domain boundar

This seems quite subjective - I have worked with services like these and would probably call that SOA where you need to split code concerns along domain boundaries. In the example above, I would probably use cloud functions or a distributed actor system. Perfect, a microservice (perhaps just service?) can be whatever you want it to be, and I don't see any reason why you shouldn't split code along technical boundaries if it somehow improves your software