Perhaps you already have ideas on how to solve for this situation, but in case it helps: forcing active record model accesses to go via a layer of indirection can help with untangling this sort of thing: https://kellysutton.com/2019/10/29/taming-large-rails-codeba...

That said, for microservice extraction specifically, a bit of creative metaprogramming/monkey patching of AR to identify & categorize your callers is probably easier.