Location-based social network Foursquare announced Monday that it has registered more than 4.5 million users. To complement its growth, the startup has also opened an office in San Francisco.

The reason? Foursquare () is vying for engineer talent in the Bay Area. And it’s not the only one — Twitter () and Facebook () have been on hiring sprees lately, and Google () has more than 2,000 open positions, the bulk of which are located in Mountain View.

Foursquare has been working out of mobile credit card reader Square’s offices for the past few months, and now they’ve “free[d] up more room for us to hire a full team of West Coast engineers,” the company explained in a blog post.