Thanks. The GetUser implementation our side is done via API and returns a 404 response if the user profile with the provided email cannot be found. This doesn’t allow the user to be added to Auth0.
At the moment we are still storing the user profile (excluding passwords) in our custom DB, so when the user signs up I register them in the custom DB first. I then use the ManagementAPI to register them within auth0. I could also do the reverse and add them to auth0 first, then create them locally (incase the email already exists from having migrated or registered in another one of our applications). We will also be bulk migrating users and generating a random password for auth0, then triggering the reset password email, or if possible a custom email template.