I applied online. The process took 2 weeks. I interviewed at Jane Street
Interview
First round I took a half hour online test which had some pretty easy conditional probability and expected value questions. Second round I had a phone interview with a trader, which took about an hour. I stumbled on one of the questions second round, and did not move on past that point.
Interview questions [1]
Question 1
Three coins are in a bag. The first coin flips heads with probability 50%, the second coin flips heads with probability 60%, and the third coin flips heads with probability 70%. I pull out a coin and flip heads. If I flip this coin again, what is the probability I will get heads?
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.