Skyrocketing user numbers likely ranks last among startup woes, but it’s a double-edged sword for Twitch. The live-streaming site, an offshoot of Justin.tv centered on video games, has seen such explosive growth that its main priority is setting up data centers around the world in order to support its 45 million viewers monthly, more than double its base a year ago. “The question is not will we grow, but how fast and how steep that growth curve will be,” Matthew DiPietro, vice president of marketing and communications, told Fast Company. Twitch announced Monday that it closed a $20 million series C round led by Thrive Capital, bringing the sum raised to $35 million. It intends to use that money to build out more infrastructure, increase its sales team, and (of course) hire more engineers. The rising popularity of eSports, or competitive video gaming, is fueling much of Twitch’s growth.