We do millions of operations like that a minute by queuing, aggregating and then committing. SQL Server's MERGE is particularly useful for it, although on our MongoDB stuff (and ironically, for player created levels) we do $incs.
I know next to nothing about this kind of stuff. If I wanted to create a stats + user generated level database system akin to Super Meat Boy (and I do) do you have any recommended resources to read?
It depends on how deep you want to go yourself. At its easiest you could just drop Playtomic [1] in, we have support for most gaming platforms.... obviously I'm quite biased towards this option. :)
If you want something more flexible and you're doing mobile you can check out Parse [2], they're a custom database with a REST, iOS and Android APIs. If you're using Flash, HTML5 or Unity3d we have a bridge that lets you use Parse through our own APIs.
If you want to get right down to the guts of it I would get a simple Heroku [3], PHPFog [4] or AppHarbor [5] account depending on what languages you're most comfortable with or learning and set up a MongoDB database over at MongoHQ [6], MongoDB lends itself very well to user created levels in my experience.
Basically you need:
1) Scripts to save, rate, count plays and list levels. You want to either authenticate the user, or more simply just obfuscate the data you're transmitting to make tampering harder
2) Some kind of logging or queueing system where you will store the plays
3) Something that will go through your logs or queues and perform the $inc operations on your levels in bulk batches rather than doing it all individually
4) Indexes on your database that match your listing requirements
On our platform the only problem has been having to perform count operations, the way we do it scores can be listed in unpredictable fashions and MongoDB is inherently bad at counts.
Aside from that the read:write ratio massively favors reading for us and caching makes that a negligible operation most of the time, and (unless like in our case you're providing leaderboards for games you don't control) MySQL and Memcache should carry you fine.
Yes, but redis is just so nice for certain applications that can be a pain in a RDBMS. Not that it can't be done, but the simplicity and performance of redis atomic counter increment/decrement is often enough for magical vertical scaling sauce. Redis is chock full of these little use cases, even when you're just using it as a "cache".
