[keycloak-user] Architecture for Multiple DB

Hi, I implemented Custom User Storage Spi, connected users db(postgresql) and also changed keycloakDS to mysql. So, I have a doubt that now my users will be stored in mysql or postgresql? And if I want to add one more user db, how the users will be merged and in which db they will be? And how about sync of all db? Thanks in advance Regards, Rohit