Jane Street values collaboration over competition. They ask open-ended puzzles with multiple valid approaches. Finance knowledge isn't required. Their coding is "simple, not LeetCode-style." They use OCaml internally but don't expect you to know it.
Interviews feel conversational. The culture is "technocratic, rationalist, jeans and t-shirts." They impose no non-compete clauses. Focus on: probability, puzzles, thinking out loud.