Want to separate data sources by user within multi-tenant services

I plan to develop a multi-tenant service.
It is assumed that each user (service user) will have a direct reference to the database of this service from an external system.
We want to separate data sources for each user so that we don't have access to other users' data.
Is there any useful way?

The environment is AWS. Application is Java SpringBoot (5.0.6)
RDS is Amazon RDS for MySQL (5.7.33)