Depends on how the library is used. If the change to the library will change how the service behaves externally (to either upstream or downstream services), the

Depends on how the library is used. If the change to the library will change how the service behaves externally (to either upstream or downstream services), then you indeed need to update them all simultaneously. However, that has the smell of poorly-defined API contracts (or poor implementations) if that is possible. Otherwise, just update to the latest library versions whenever you touch a codebase.