Strategies for AB testing

planning for AB testing. Let’s assume we have two versions of the application V1 and V2. V1 has its own set of application and DB changes and same case with V2(so V1 has its own database and V2 has its own database – not sure this should be the way or some other way). Now AB testing has been initiated with 10% of the users hitting V2 and 90% of users hitting V1. after completion of the test, we have decided to roll the V2 to all the users. applications can be rolled to all the servers but what happens to the database? what is the approach that has to be taken?

Source: StackOverflow