Initial communications were through my hiring manager. The company is a very small start up. After the initial 1:1 phone interview with my hiring manager, I then had a follow-up on-site interview that consumed most of a working day. I met with everything that I'd be working closely with, as well as with the CEO of the company. The CEO gave me the most challenging questions, technically and otherwise. The interview with my hiring manager was a bit strange. I got a sense that his personality was brusque, but didn't think about it too much, since I liked the rest of the people and I liked the job.