If several databases/services are so tied together that they need to be updated/rolled back at the same time, then they belong to the same service/database. Th

If several databases/services are so tied together that they need to be updated/rolled back at the same time, then they belong to the same service/database. There will be times when you trade data consistency for performance/scalability, i.e. in a scenario where you are breaking user actions away from the main user service, if a user is deleted but deleting from user actions failed, you don't roll back the user delete. Either just let the invalid data sit in user actions database, or do separate clean-ups periodically.