A shared database is an anti-pattern in distributed systems.

Similarly, distributed transactions (ala. DTC) is an anti-pattern.

Distributed systems aren't hard. They're just different.

Then again, sometimes it's advantageous to identify parts of your system where aspects of state can be safely decoupled. And in which having them reside in disparate systems (and yes, sometimes be inconsistent or differently available) might actually be a better overall fit.

You completely lose the concept of transactional integrity, so you will have to work around that from the start.

Then again, sometimes your state changes not only don't need to be transactional; it can be disadvantageous to think of them that way.

Depends, depends, depends.