I did an initial 30 minute phone screen with the lead engineer. He asked good questions about my work history and was very engaged. I went in for a in-person interview with him a few days later, which lasted 2-3 hours. Again I thought his questions were good ones. This time they were related to specific technical problems related to the business. I worked through them on the board while he listened and provided occasional hints. At the end of the interview the CEO came by to introduce himself and we chatted briefly about the company history and business model.