Requesting development advice

I have a scenario where a third party app will manage users and update their info using the API.
Currently I query all users, then pick the one I need from the array and update it.

I believe this is not good for performance when the list gets big, and a new endpoint for searching by email/username would be ideal.

Any advice/tips/ideas on how to code this new endpoint?

Why can't you just get users by id? That's what we do in the official app.

This external web app does not know the user id, only email.

I guess I could also build a backend service for this external app that connects to the same database to query user data. Is there a problem if I take this route? Don't wanna mess with the db data consistency

I would definitely recommend using API to avoid caching problems.

Makes sense. I'll have something like /API/users/email/{email} then. Should be fairly simple to implement in the UserResource class.