Jane Street · Software Engineer (New Grad)
Jane Street's new-grad SWE loop is unusual: it weights probability, mental math, and clear reasoning as heavily as coding, and it explores how you think rather than whether you've memorized patterns. Expect problem-solving and estimation puzzles, probability and expected-value questions, trading/market brainteasers, and a coding round where reasoning out loud matters more than a specific language (they use OCaml heavily but teach it). Interviewers care about depth, honesty, and how you handle a problem you can't immediately solve.
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What this interview tests
- Probability, expected value, and conditional reasoning
- Fast, clean mental math under mild pressure
- Brainteasers and market/trading games under uncertainty
- Updating estimates honestly on new information
- Algorithmic reasoning (recursion, invariants, data structures)
- Composure and honesty on unfamiliar problems
Common question themes
Expected-value and conditional-probability puzzles
Mental-math and estimation problems
A betting / trading game with changing information
"How would you price or bet on this uncertain outcome?"
Algorithmic reasoning problem (language-agnostic)
A combinatorics or dice/cards probability question
Modeled on a public Jane Street new-grad SWE posting