[keycloak-user] Moving from two legacy identity systems to keycloak

Hi, I recently joined a company as a software developer. The company has merged with another one a couple of years ago and that lead to lot of migration problems. We are now looking into unifying our user base under the same store and provide a single login/password for all products. With this in mind I started looking for a solution that would help us: and I found keycloak. I have been playing around with it but the truth is that I’m not very confident on how to approach such Herculean task. I have thought of a couple of options: 1) build a spi for each legacy systems and let keycloak talk with such systems for current users but register new users on keycloak’s own data store 2) have my legacy systems programmatically create a new user on keycloak every time someone logs in (as in slowly migrating users from the legacy datastores into keycloak). Bear in mind that either way I need to still be able to expose at least the original Id for the users on keycloak so that other systems that rely on them can still work. Any help around this is much appreciated! Thanks!!!! -- Regards, Leandro Nunes