Informational phone call. 45min technical skype interview (using coderpad.io) a few days later. A week(ish) later, 5 45min/1h interviews onsite. Covered various topics including technical implementation of a system, API design (and partial implementation), previous experience designing systems. I appreciated the interview focus on designing good interfaces. Before the interview I was provided with a "How to do well in a Square Interview" document. It accurately represented the experience I had in the interview, with no surprises. Went for lunch at a nearby restaurant with a couple of the employees to break up (long) the interview onsite interview process.