Synchronize tables in SpringBoot multitenant architecture

I have a SpringBoot application running on a multitenant architecture.

I've two databases Admin and Client (both are MySQL) and both these databases have a User table

Client can add users to the User Table but I need them to get synchronized in the User table of Admin database.

Is there a way I can achieve this?

I've read about flyway migrations but I think it works more on database schema changes and not values.

Please ignore my mistakes as this my first question, any help would be appreciated.

This looks like a solution to your problem:

SymmetricDS is software that replicates relational database tables between multiple databases. It can also be used to replicate files and directories between multiple hosts. It uses a light-weight, web-based protocol to send and receive data, which makes it easy to work with firewalls. Replication is done in the background asynchronously, allowing data changes in offline mode. It supports most commercial and open source database platforms.

How does it work?
Triggers are installed in the database to guarantee that data changes are captured. This means that applications continue to use the database as usual without any special driver software. The triggers are written to be as small and efficient as possible. Routing and syncing of data is done outside of the database in the SymmetricDS process.

SymmetricDS supports many databases and can replicate across different databases, including Oracle, MySQL, MariaDB, PostgreSQL, MS SQL and many more.

https://www.symmetricds.org/docs/faq

You need to create some event from the flow where client adds user to the User Table.

If this "client" flow is in same java service then you can make use of Spring's Asynchronous Event Handling or have a method(which does the data copy) marked with @Async. This ensures the data copy happens in separate thread.

If the "client" flow is in different java service, then any publisher-subscriber model can be used (some opensource frameworks available are kafka, rabbitmq etc).

Now to connect to two datasources at the same time, Spring's RoutingDataSource will come handy in this scenario as it works on "lookup key" to choose the datasource. Or else you can hardcode two datasource beans in your config (since it is fixed in your case).