Definitely what I'm saying. But the point about libraries which don't own data is also valid and those can be useful as services in some cases. Particularly when we are talking about something like a set of business rules to follow.
At a bare minimum, if there's some sort of mutable data involved then I think there should be a single service that owns it. But I could also see reasons to create services which don't involve mutable data.
It does somewhat come down to complexity though. Like, for example, I think a "matrix multiplier" service would be silly. Or even just a general "do-math" service. But a service that, for example, takes in raw video and spits out compressed video? Now we are talking about something that probably is better as a service and not a library as you likely want to do things like control encoding values and standards system wide.
Just a little about my background. The systems I worked on, for example, shared user information using the `user-lib` library which contained all the details of how to fetch (and insert, and update) a user from the users table. Many services used that library to pull user information which has been a mess to untangle.
At a bare minimum, if there's some sort of mutable data involved then I think there should be a single service that owns it. But I could also see reasons to create services which don't involve mutable data.
It does somewhat come down to complexity though. Like, for example, I think a "matrix multiplier" service would be silly. Or even just a general "do-math" service. But a service that, for example, takes in raw video and spits out compressed video? Now we are talking about something that probably is better as a service and not a library as you likely want to do things like control encoding values and standards system wide.
Just a little about my background. The systems I worked on, for example, shared user information using the `user-lib` library which contained all the details of how to fetch (and insert, and update) a user from the users table. Many services used that library to pull user information which has been a mess to untangle.