Interesante artículo: http://cacm.acm.org/blogs/blog-cacm/51564-extreme-agility-at-facebook/fulltext

 

Facebook’s architecture is based on typical hierarchical PHP External Link Web application model with a layer of data caching and extracted services components.  The caching layer is done via the stable and fast memcached External Link open source software on top of one of the largest installation of MySQL External Link.  The caching layer is so critical to Facebook’s success that Facebook is now one of the main contributors to memcached External Link.