I applied online. The process took 1 week. I interviewed at Jane Street (London, England) in Apr 2018
Interview
Interview process was somehow different. Interviewer was really kind and only asked probability questions after short introduction. Questions were not that hard since it was the first round phone interview.
Interview questions [1]
Question 1
I'm flipping three coins. If all three are the same (all heads or all tails) then I will get 10 dollars and I may finish the game. If it is not the case then I might ask to flip any number of the coins again (to flip one of them or two of them again, etc.). What's the expected gain by playing this game?
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.