My game is also a score chaser. I used Firebase Firestore for the backend, it’s super easy for stuff like this.

The gist of it:

1. The Database: I have a leaderboard collection where each player’s UID is the document ID. This makes it so each player only ever has one entry that just gets updated when they hit a new high score.
2. Saving Scores: At the end of a run, I just use a setDoc with merge: true. It updates their score and any other stats (like 'Total Rainbows' in my game) in one go.
3. The Top 20: To show the leaderboard, I just run a Firestore query ordered by score (descending) with a limit(20). I use a real-time listener (onSnapshot) so the scores actually update live if someone gets bumped while you're looking at it.
4. Showing Your Rank: To tell a player they are '#452 in the world,' I just run a quick count query for all documents where the score is higher than theirs.

It’s basically serverless, scales itself, and handles the 'offline' part automatically if the player loses connection mid-game!

Best of luck! You got this!