I applied online. The process took 1 week. I interviewed at Jane Street (London, England) in Oct 2017
Interview
The interviewer was very friendly which helped take some pressure off me. During the interview process he didn't indicate whether I got an answer right or wrong, though there were times when he asked follow-up questions to improve my answer. He answered my question at the end nicely and in details. Just got invited to second round.
Interview questions [1]
Question 1
First round: basic probability, combinatorics.
A bear wants to catch 3 fish from a river. when he has caught 3 fish, he'll leave. when a fish comes, there is a 1/2 chance he'll catch it. what's the probability that the 5th fish will not be caught?
The process began with serveral online tests for maths and logic. They gave a personal interview to get to know the candidate better and evaluate fit for the company/role, then held a technical interview covering maths and logic problems.
Fun and filled with unexpected questions. The questions rely on fast thinking and fast calculations, and sometimes intuition because there is no sufficient time for me to work through the whole problem.
We started with a bit of small talk, followed by some probability questions. Ended with some basic algebra questions, Make sure to ask questions if you have any. Good experience, feels like the interviewer was trading.