It is a series of interviews with pairs of people, each asking something different. They want to see your technical prowess, your thought process, and how you tackle a problem while optimizing for what is best for business. The questions themselves were all technical and/or business related. The questions don't seem very challenging, but your answers need to be very strong, and that is where the difficulty lies. Most interviewers are very friendly and helpful, and they will help you stay comfortable. This is not a huge company, but they have many applicants. They have their choice of who to hire, and it is probably worse for them to turn down a possibly good employee than it is to hire on a bad one. Because of this, you need to be highly compatible or strong in many areas (personality, work culture, technical ability, business acumen), and you will need to get that across in your interviews. I'm sure they also hire rock-stars who would be core to improving their business.