I received two preliminary calls before being granted an interview, roughly 10 mins a piece. The first call is just with an HR rep and the second with a hiring manager. I think they just want a feel for you on the phone. Questions like " How do you stay motivated?" Typical interview type questions. The interview was less than an hour and ended with a tour of the office which is nice, lots of perks, free food and drinks throughout the day, catered meals etc.