The process took 2 weeks. I interviewed at Jane Street (New York, NY) in Sept 2016
Interview
I applied online to the Software Developer role, they said I may be better suited to a Trading role.The process took 2 weeks. Interviewer was really great, he gave hints and was really helpful
They tend to examine the logical thinkers that can communicate clearly and concisely, and some problem-solving exercises intended to explore how you gather and apply new information, very different from other tech companies' interviews.
Initial application and online assessment. Had a first round behavioral interview where they asked me about myself, my experiences, and a couple of brain teasers. The interviewer was very nice.
Phone interviews (at least 3) - questions were of mixed difficulty (some pretty hard) but the interviewers were friendly and they gave helpful hints. Kind of fun - review probability and game-type questions.