Process, Questions & AI Prep Tips
Jane Street is one of the world's leading quantitative trading firms and one of the largest market makers in equity and options markets. Engineering interviews are exceptionally rigorous, combining deep computer science fundamentals, functional programming (OCaml), probabilistic reasoning, and a unique trading domain knowledge component. Jane Street is known for having one of the most intellectually demanding hiring processes in the technology industry.
A 30-minute call assessing your general background, interest in financial markets, and fit for Jane Street's collaborative, intellectually rigorous culture.
A 60-minute interview with challenging algorithm and functional programming problems. Expect OCaml or a functional style in any language.
A session focused on probability puzzles, expected value calculations, game theory, and quantitative reasoning that simulates trading decision-making.
Another technical session exploring algorithmic problem-solving in more depth, often with recursive and functional solutions emphasized.
A discussion exploring market intuition, how you think about trading strategy, risk management, and your understanding of financial markets.
You are offered a game: flip a fair coin and win $2 if heads, $1 if tails. How much would you pay to play? What if you play 100 times?
Design a market data processing system that handles 10 million price updates per second with sub-microsecond latency.
How would you build a risk management system that calculates real-time portfolio Greeks (delta, gamma, vega)?
You have two envelopes, one with double the other. You open one and see $100. Do you switch? Why?
Design an order matching engine for an options exchange that processes 1 billion orders per day.
How would you implement a functional data structure for an order book using immutable principles?
A stock has expected daily return of 0.1% and daily volatility of 2%. What is the expected return over 252 trading days?
Design a distributed trading system where consistency is more important than availability.
How would you build a position reconciliation system that ensures trading books match across all systems?
Explain the Black-Scholes formula and its assumptions. What happens when those assumptions break?
Learn OCaml seriously — Jane Street uses OCaml for nearly all of their trading systems and interviewers will assess your functional programming depth. Even basic OCaml proficiency is expected.
Study probability and expected value deeply — Jane Street's probability rounds are notoriously challenging and require comfort with conditional probability, Bayes theorem, and combinatorics.
Read Heard on the Street (Crack) and Mark Joshi's probability puzzles — these cover the style of quantitative reasoning problems Jane Street asks.
Understand basic options concepts including calls, puts, delta hedging, and how market makers manage risk.
Jane Street values collaborative problem-solving — they are explicitly interested in how you think through problems, including talking through your reasoning out loud.
Practice mental math for quick approximations — trading decisions require rapid quantitative estimates.
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