Best practice to associate front-end data with user IDs

Hello everyone,
I’m working with an Auth0 SPA application developed in React. In the application I’m developing, a logged user should be able to save a list of “preferred items” that are served to my front-end via an API call to an external DB.

I’m trying to figure out the best approach to handle the association of a user ID to its saved lists. I’ve been digging in documentation, coming across user_metadata and the User Management API as (seemingly) the best options.

My first train of thought is to securely send user IDs to my external DB, store them there, and whenever a user saves a list on the front-end, send the user ID + the saved list.

I’m a newcomer to Auth0 and I don’t want to overcomplicate the solution. I reach out to the community to see if I’m on a good track and what would be the recommended+simplest approach to deal with this situation.

Thanks in advance.