I was interviewed by their hiring manager on the phone. He asked a few introductory questions, and what I have done so far, and then dived into the technical questions. He asked whether I knew about Java garbage collection. Then he asked me to describe an algorithm. I described mark and sweep, and he asked how to get around circular references when using mark and sweep. Next he started asking some OS questions: What was the difference between processes and threads, how do caches work, etc.