You each rate on your own. Neither of you sees the other's answers.
This demo shows title cards until it has a TMDB key. Paste one here and it will fetch the real poster art. The key stays in this browser and goes nowhere else. In the deployed version it lives on the server instead and the page never sees it.
Ratings live in this browser only, until the database exists. Clearing your browsing data would wipe them. Save a copy and they can always be restored.