Nice work and some thoughs

Yeah, my thoughts are that something like this would be perfect for school/lab/office tournaments. Just give it a new name in the client, set up a participants list somewhere and away you go.

In the free tier I'm not really going to run out of disk space any time soon, a rumble of 300 bots comes out at around 2MB, it's the database writes which are the killer. From what I can tell, App Engine pricing starts at $2.10 a week for the minimum paying tier. That gets you quite a bit more quota than the free tier, which probably should be enough for everything, pretty much forever, without crossing that $2.10 limit. For now I'm going to see how much I can push the free tier, though.

I still have a bunch of optimisations I need to make - like not pulling all of the rumble data into memory just to serve the rankings page (it's all cached, doesn't affect my quota, just speed) - which should make it more snappy both on the main rankings pages and on the RatingDetails page the RR client queries occasionally.

A hidden feature: if you add timing=1 as an argument into your GET for any of the pages it summarises the timing breakdown for CPU usage at the bottom of the page and lets you know how many bots were pulled from cache vs. from the datastore.