Nice work and some thoughs

The problem isn't so much total storage space, but that I'm limited at 50k writes per day. Each bot counts as 2 writes, so effectively I have 25k updates I can do. I've figured out a caching scheme so that each melee battle comes out to 10 updates (1 per bot) instead of 45 updates (1 per pairing). I also need to update the total rumble battles count and the user upload count, so that leaves a bit of overhead, meaning I can have ~2000 melee battles per day uploaded.

I'l see what ratings systems are feasible..

Batch updates are more useful in a limited environment like that. Maybe it´s time for a refactoring in the upload protocol (1 update per batch upload), even if it breaks backward compatibility.

I've actually figured out a sort of temporary caching between requests where I wait for bots to accumulate a certain number of pairings before pushing them to disk. I don't think it's necessary to re-work the rumble upload protocol yet. One thing I would like the rumble to tell me is how many bots are in a melee battle though. Right now I just have it hardcoded at 10. It would help with my caching if I knew how many they were uploading per battle.

Flush them to the database on a period basis (constant number of commits regardless of number of uploads) instead of being per number of uploads?