Build.one integrated DB and DBs integrated through PASOE (MSSQL, Oracle) are transaction save with roll backs etc.
But it is fair if you have Progress OpenEdge and Salesforce data in one screen, and you save in both from one screen, there are scenarios that one could write to one but not the other.
The benefit of Build.one and the ProCode is that you can protect against consistency issues by running sanity checks and extend beyond the capabilities the involved systems provide as is.
Solve for a use case with three Core Systems:
For LN we did SalesFoce and NaVision and we have a Neuanlage Funktion, ueber alle drei System. All three system are connected to B1, messaging Bus, ProCode functionality checks consistency. All systems send event to B1, Neuanlage von Navision, if an edit occurs in one, B1 propagates to the other. What is the MessageBus? ConnectPlaza mit ActiveMQ, JMS connectoren sind allgemein gut anzubinden. Validation of transaction reads and writes can be detected with, conflicts are rare but other times thousands of issues come with it.
But, make sure you know if the complexity introduced is needed, sometimes the last wins is sufficient