Jane Street interview questions

Showing 31–47 of 47 results

• Optimize trade PnL table updatesHard

  Design an incremental PnL tracking engine that efficiently aggregates realized and unrealized profit-and-loss across overlapping predicate views under high-frequency trade and price tick updates.

  Jane StreetSoftware EngineerCoding & AlgorithmsOnsite
• Payout-Split Formula Where Every Step Is a Whole Positive ShareMedium

  Write a parser and evaluator for arithmetic formulas that describe splitting a prize pool into whole-unit shares, where every intermediate computed amount must be a positive whole number or the entire formula is rejected. Tests recursive-descent parsing combined with evaluation rules where a single bad step invalidates the whole result.

  Jane StreetSoftware EngineerCoding & AlgorithmsTechnical Screen
• Predict future time-series valuesHard

  This interview question evaluates ML product requirements, data/labeling, modeling, serving architecture, evaluation, monitoring, and trade-offs in a realistic interview setting. A strong answer for Predict future time-series values states assumptions, handles edge cases, explains trade-offs, and shows how to validate the result clearly.

  Jane StreetMachine Learning EngineerML System DesignTechnical Screen
• Pricing a Mystery Money Box: Expected Value, Adverse Selection, and CompetitionMedium

  This question evaluates probabilistic reasoning and economic-incentives competencies, including expected-value calculation, risk-neutral decision-making, adverse selection, and surplus division in bargaining contexts.

  Jane StreetQuantitative TraderMachine LearningTechnical Screen
• Process One Million Quote Updates per SecondMedium

  Design a low-latency market data processing engine capable of ingesting 1,000,000 quote updates per second across multiple exchanges, maintaining global best bids and asks, and triggering immediate cross-venue arbitrage alerts.

  Jane StreetSoftware EngineerSystem DesignTechnical Screen
• Reach a Target Using Each Number At Most OnceHard

  This question evaluates the ability to construct arithmetic expressions from a multiset of numbers and reason about combinatorial search, operator composition, parenthesization, and exact rational arithmetic under constraints.

  Jane StreetSoftware EngineerCoding & AlgorithmsTechnical Screen
• Sealed-Bid Auction for a Box of 200 Coin Flips (and an Informed Opponent)Medium

  This question evaluates understanding of probability and expected-value reasoning, auction and game-theoretic strategic thinking, Bayesian inference under asymmetric information, and quantitative decision-making relevant to a Machine Learning-focused data scientist role.

  Jane StreetQuantitative TraderMachine LearningTechnical Screen
• Snake Game: Minimum Moves to Reach the AppleHard

  This question evaluates proficiency in state-space modeling, constrained grid pathfinding, and dynamic collision handling, testing skills in shortest-path reasoning and movement legality within the Coding & Algorithms domain; the level of abstraction is practical application of algorithmic techniques to simulate evolving game states rather than purely theoretical analysis. It is commonly asked in technical interviews because it requires reasoning about evolving constraints and reachable states, demonstrating an applicant's ability to model complex movement rules and perform effective search under limited grid and body-size constraints.

  Jane StreetSoftware EngineerCoding & AlgorithmsTechnical Screen
• Solve probability and game-theory puzzlesEasy

  This set of puzzles evaluates probabilistic reasoning, Bayesian inference, expected-value optimization, optimal stopping, and strategic game-theoretic reasoning under uncertainty and asymmetric information, situated in the Statistics & Math domain.

  Jane StreetQuantitative TraderStatistics & MathTechnical Screen
• Solve queue switch and coin change puzzlesMedium

  This two-part question evaluates probabilistic reasoning about expected waiting times with random queue switching and combinatorial/algorithmic counting for coin-change combinations, testing skills in probability, expectation and order statistics as well as combinatorics and dynamic programming within the Coding & Algorithms domain.

  Jane StreetQuantitative TraderCoding & AlgorithmsOnline Assessment
• Sort trade executions into a canonical orderEasy

  This question evaluates a candidate's ability to enforce deterministic ordering and data normalization of time-series trade execution records, testing competencies in multi-key sorting, tie-breaking logic, and performance with large inputs.

  Jane StreetSoftware EngineerCoding & AlgorithmsOnsite
• Stack Machine Interpreter with Typed Int and String ValuesEasy

  This question evaluates understanding of stack-machine semantics, runtime type representation and preservation of distinct integer versus string values, plus handling mixed-type ADD behavior and output semantics.

  Jane StreetSoftware EngineerCoding & AlgorithmsTechnical Screen
• Turning Interview Code into a Reusable Library or APIMedium

  This question evaluates a candidate's skills in software design and engineering practices, including modularization, API and library interface design, documentation and typing, robustness and error handling, testing, packaging, versioning, and state/transport considerations.

  Jane StreetSoftware EngineerSoftware Engineering FundamentalsTechnical Screen
• Two Opaque Boxes: Place or Take for Maximum Expected PayoffMedium

  This question evaluates probabilistic reasoning, expected-value analysis, and sequential decision-making under uncertainty, testing competency in stochastic modeling, combinatorics, and optimization.

  Jane StreetQuantitative TraderCoding & AlgorithmsOnsite
• Validate order book data across multiple databasesEasy

  This question evaluates a candidate's competency in designing data-validation and reconciliation systems for financial order books, including defining invariants, ensuring cross-database consistency, and handling edge cases like partial fills, cancels, out-of-order events, duplicates, and replayed messages.

  Jane StreetSoftware EngineerSystem DesignOnsite
• Which Dice Game Wins More Often: One Six in 4 Rolls, or Double Sixes in 24 Rolls?Medium

  This question evaluates probabilistic reasoning and statistical intuition, focusing on independence of trials, event probability versus expected value, and the ability to compare probabilities of rare events.

  Jane StreetQuantitative ResearcherSoftware Engineering FundamentalsOnsite
• Write an Interpreter for a Small Language with Load, Store and ArithmeticMedium

  Practice writing an interpreter for a small language with load, store and integer arithmetic instructions, using an assumed stack-based specification. It tests parsing source text into instructions, executing them with correct operand order, and reporting errors such as stack underflow, undefined variables and division by zero.

  Jane StreetSoftware EngineerSoftware Engineering FundamentalsTechnical Screen