there are system An and system B.
system An owns database An independently, and system B owns database B.

system An and system B share a set of user information database, database C.
Database C stores all the information about the user, such as name, birthday, gender, etc.

question:
when system A wants to jointly check user information (for example, system A queries the details of all users under an organization), these functions can only be achieved through cross-database joint search (database An and database C).
this will make the code look ugly. Is there a more reasonable way to query or design the system architecture?

original question:
idea of sharing user information among multiple subsystems of https://codeshelper.com/q/1010000015878010">?