Zynga, the maker of popular social games including Farmville, CityVille, and Mafia Wars, has made a major shift in where it gets the computing horsepower for its more than 227 million monthly active users, in effect, upending its dependence on Amazon Web Services' infrastructure.

"Nearly 80% of our daily active users were hosted in the (Zynga) zCloud at the end of the year, compared to just 20% at the beginning of the year," said John Schappert, Chief Operating Officer, during the earnings call Tuesday.

That would still make Zynga one of the largest implementers of hybrid cloud computing, building regular use of the public cloud into its IT staff's planning for how it will add to and use its own data centers. But it also represents how quickly the supplier of social networking games is revising its approach.

The shift toward in-house operations will be announced during Zynga's fourth-quarter and full-year 2011 earnings call, scheduled for 5 p.m. Eastern Tuesday, after the close of markets.

InformationWeek disclosed last May, prior to Zynga's initial public offering, that the game maker had begun to use Amazon's EC2 cloud as its launchpad for new games with the 2010 release of CityVille, one of its most successful games

[ Want to learn more about Zynga's approach to the hybrid cloud? See Zynga's Unusual Cloud Strategy. ]

Zynga had already switched the burden of supporting many of its peak daily active users into Amazon's EC2. With CityVille, Zynga decided to conduct the whole launch in the cloud and let its rapid expansion occur there, if the game was destined to succeed. Once it slowed to a predictable growth path, Allan Leinwand, Zynga's infrastructure CTO, explained at the time, the game's operation would then be brought back in house to data centers that Zynga either owns or leases.

CityVille got off to a fast start and Zynga brought it back to data centers purpose-built to support its new zCloud infrastructure, an Amazon-like setting. The zCloud functions as an efficient host for Zynga's gaming infrastructure, and its smooth operation paved the way for more of Zynga's external cloud activity to return in house.

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