Welcome to the Auth0 Community!
There are different ways to approach synchronizing your external user DB with the Auth0 user store.
- You can use periodic syncing via Bulk User Exports or Manage Users Using the Management API
- Sync on login via Login Flow Actions (be careful, this runs on every authentication and requests can slow down your login flow)
- Or sync with your DB when you receive a valid token in your app.
Alternatively, you can use your DB as the source of truth with Custom Database Connections, but this will limit you to only username/password connection and no third party IdPs like Google or Github.
Let me know if you have any questions.