Met them at university career fair -- was surprised to see an HFT firm at my small school! I had competing offers with upcoming deadlines when they first got back to me. They agreed to move quickly and sent me a programming test which seemed to test attention to detail and ability to operate under time pressure (probably more important in trading than a pile of "have you seen the n log n solution before" algorithm questions). Next I chatted with a recruiter to get a sense of what we were both looking for. Decided to interview for a NYC trading role and had a technical call with a trader later that day. He asked me a nifty math question and then answered some of my questions. They invited me to an onsite that Friday with all the arrangements handled. The day started with some snacks and an IQ test. Next I spoke 1-1 with several traders, their manager, and a senior quant type. All interviews were very informal and actually enjoyable. Hard questions but no BS ( i.e. no existential questions, good cop-bad cop, bet on your answer, etc). Due to my deadlines I didn't get a chance to meet with the CEO but they extended an offer the next day. Overall, an efficient and enjoyable process. I would enjoy working with everyone who interviewed me and that's why I took the job. The people seem humble but very capable.