- Multiple execution environments
- Complexity in communication between services
- Managing the versioning of each service and it's dependent services.
Although services are easily to scale and change independently, they are hard to reconfigure globally, which means the application as a whole is hard to change...
Often switching to microservices means reducing the complexity of communication between teams at the expense of increasing the complexity of communication between services.
There is common release process, but with proper infra in place, that shouldn't be a problem.
Suppose you'd like to push code change to production for your monolith - how do you know that someone else's change 1) is ready to to production together with yours 2) does not affect your module. Typically these can't be answered easily - and so release process is converted to manual testing and scheduled (and often slow) releases.