Windows Server AppFabric is Microsoft’s implementation of a distributed cache, the most well-known example of which is memcached, as used on LiveJournal, Wikipedia, Twitter, etc.

Windows Server AppFabric provides a distributed in-memory application cache platform for developing scalable, available, and high-performance applications. AppFabric fuses memory across multiple computers to give a single unified cache view to applications. Applications can store any serializable CLR object without worrying about where the object gets stored. Scalability can be achieved by simply adding more computers on demand.

There is a good introduction to distributed caching on MSDN<[/inlineexternallink] written by Iqbal Khan of Alachisoft, who wrote their NCache product several years before Microsoft came up with AppFabric.

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