Redis is a key-value database. It is similar to memcached but the dataset is not volatile, and keys can be strings, exactly like in memcached, but also lists and sets with atomic operations to push/pop elements. In order to be very fast but at the same time persistent the whole dataset is taken in memory and from time to time and/or when a number of changes to the dataset are performed it is written asynchronously on disk. You may lost the last few queries that is acceptable in many applications but it is as fast as an in memory DB (btw the SVN version of Redis includes support for replication in order to solve this problem by redundancy). Replication and other interesting features are a work in progress (Basic master <-> slave replication implemented in Redis SVN). Redis is written in ANSI C Redis is pretty fast!, 110000 SETs/second, 81000 GETs/second in an entry level Linux box.
Traditional methods for protecting community from the effects of scale and poor behavior are now manifestly unfeasible. Raising barriers to entry, relying on the assumption that users will maintain only one registered account, and placing faith in the ability of admins and user moderation to reproduce a forum's organic culture are all easily circumvented, gamed, and/or ineffective when faced with the problems of scale. Moreover, they tend to reinforce self-destructive behaviors, by increasing returns to the most persistent rather than the most constructive, reinforcing groupthink, and providing ample targets for trolling and griefing. This article attempts to fundamentally rethink what constitutes community and society on the web, and what possibilities exist for their maintenance and reconstruction in the face of scale and malicious users. The recommendations reached, after analyzing the weaknesses of the web forums we all know and love