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One big cache for everything. I used to have a queue for each rumble that would fill up, and each time a bot had over X battles it would be written to the database. Of course, when the nanorumble only gets 1/10th or less the battles of the main rumble, the bots in it are more likely to be evicted, resulting in incomplete and asymmetric pairings. So I've just rewritten that section to keep just two queues (only split between 1v1 and melee), and bots are written as a batch as soon as the queue is a certain size. That way, even bots getting less battles will still be written because they are all pushing each other through, so it should stabilize better. Unfortunately I couldn't do this before because I was too limited with writes.