Zynga is in the business of "big data," said CTO Cadir Lee, meaning it's constantly wading through vast quantities of information about its customers, to understand their behavior. It does this partly to match players with similar skill levels, in games like "Words with Friends," he said.

The company has been known to deploy 1,000 servers in a single week to support new, fast-growing games, he said.

Zynga, which said earlier this year it will file for a public stock offering, is still the top maker of games on Facebook. It has almost 77 million monthly active users for CityVille, although that is down from an all-time high of 111 million, .

FarmVille has about 35 million monthly users, also down significantly from its all-time high. But "Adventure World," which went live only last month, is already the number-three game, AppWorld says, with 35.6 million monthly users.