A Microsoft official nonetheless emphasized the company's embrace of open source paradigm, even if it wasn’t necessarily for altruistic purposes. Microsoft has had a "contentious" relationship with open source proponents but "things are really changing," Stuart McKee said. McKee, who focuses on governmental customers for Microsoft, offered his perspectives in a keynote speech at Open Source Business Conference in San Francisco. Microsoft has contributed 20,000 lines of device driver code to Linux kernel so Linux can run on Microsoft's Hyper-V, noted Robert Duffner, who also was present at OSBC. Among other examples of Microsoft's embrace of open source cited by McKee included Microsoft.web site for Microsoft Web platform, which features 23 open source apps out of a total 25 apps. Also, Apache software, MySQL database, and PHP all run on Windows Azure cloud platform, McKee said. "We rely on Varnish project. Varnish is an incredible open source cache," Recordon said. Billions of requests are served through Varnish everyday around world on Facebook, he said. To boost PHP performance on the site, Facebook developed an open source technology, HipHop for PHP, which transforms PHP code into highly optimized C++, said Recordon. Facebook also uses open source Memcached distributed memory object caching system and the MySQL database, Recordon said. Memcached, he said, "is sort of like that magic pixie dust" for scalability.