External IDP user account linking with existing users only stored in external user database

We are using Keycloak as Identity brokering, Users are authenticated at external IDP only. Our user case is that Keycloak must link IDP account with existing users stored in external database such as mysql, but must not include any other execution such as confirm link existing user or email verification.
First Broker Login flow auto linking by Create User If Unique execution flow is best fit but if we can have similar execution flow to link with external DB only and Keycloak must not create or link with it’s own DB.
Please suggest how can I achieve this use case.

Can anyone please suggest the appropriate solution?

Hi,

to use external databases you’ll need to implement an User Storage SPI. Take a look at the docs if you’re going to do it.

When the custom User Storage is running, linking is (somewhat) automatic. You can disable checks when linking accounts too.