Jane Street Software Engineer interview prep | RoundHound

Jane Street Software Engineer interview prep | RoundHound

How to prepare

Choose one language and refresh its basics
Pick the language you know best. Write from memory the common operations for arrays, hash maps, sets, queues and sorting. Also write a tree traversal and a graph traversal. Write real, runnable code, not pseudocode.
Jane Street asks for real code in the language you know best. It gives no extra credit for OCaml. It expects you to know basic data structures and APIs in that language.
Company researchPreparing for a Software Engineering Interview :: Jane Street Interviewing :: Jane Street Software Engineering Mock Interview :: Jane Street
Prepare a spoken opening for each problem
Write a short script with four steps: restate the problem, name two approaches with their trade-offs, name the edge cases (empty, single item, duplicates), then start coding. Say it once on one problem you pick.
One experienced candidate blamed a poor first data structure choice and silence during coding for a rejection. A fixed opening helps you share your reasoning from the start.
Company researchPreparing for a Software Engineering Interview :: Jane Street Jane Street Blog - What a Jane Street dev interview is like Jane Street Software Engineer Interview Experiences 2026
Write your "I don't know" sentences
Write two plain sentences you can say when stuck. Example: "I know X. I am not sure about Y. I would test Y by doing Z." Also decide how you will state time and space complexity and one improvement.
Jane Street tells candidates to know what they do not know. A ready phrase stops you from guessing under pressure.
Company researchPreparing for a Software Engineering Interview :: Jane Street Jane Street Blog - What a Jane Street dev interview is like

Then try the round

You have chosen your language, listed its main data structure operations from memory, and written your opening script and your "I don't know" sentences.

Resources to focus on

Preparing for a Software Engineering Interview :: Jane Street
Sections on the structure of SWE interviews, what Jane Street looks for, and how to prepare.
Check the stated format and expectations. Use them to shape your opening script.
Software Engineering Mock Interview :: Jane Street
The practice advice text: use a timer, talk through ideas, write out the easy parts. The video itself was not reviewed.
Copy the habit of talking through your ideas while you write code.
Asynchronous Technical Interviews: Reducing the Effect of Supervised Think-Aloud on Communication Ability
The abstract only. It reports that being watched often makes candidates explain their reasoning less well.
Expect talking while coding to feel hard. Record yourself on one problem to hear how clear you are.

Confirmed · 19

Jane Street's official pages describe a technical interview over Zoom, then final-round interviews in person at one of its offices. Both stages focus mostly on collaborating on coding problems.
Candidates write real code, not pseudocode, in the language they know best. Jane Street gives no extra credit for OCaml and says not to use it if it isn't your strongest language.
Jane Street says it prefers open-ended problems with several reasonable approaches, and that the journey through the interview matters more than the final solution. One of its tips is to know what you don't know.
Jane Street's current preparation page says software engineers aren't asked mental math, math olympiad questions or logic puzzles. A 2020 Jane Street post said the same about math and probability.

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A 2020 Jane Street post says almost everyone does one technical phone interview, then an onsite with 2 to 4 technical rounds. London candidates may first do a HackerRank round. This may describe an older process.
Jane Street says candidates should be comfortable with basic data structures and APIs in their chosen language. Its mock interview page suggests LeetCode and HackerRank for algorithmic practice, while noting their questions aren't exactly what Jane Street asks.
Jane Street offers a software engineering mock interview video that uses a retired question. It warns that much of the interview information online is outdated or wrong.
A senior candidate's report from December 2024 says the software engineer process was not math or brainteaser heavy at all. The same loop included a project deep dive alongside coding rounds.
One aggregator's 2026 summary of reports mentions an early technical screen with math and probability questions, brainteasers and data-formatting tasks. This conflicts with Jane Street's own guidance, and the roles behind it are unknown.
One new-grad software engineer in New York (January 2025, no offer) reports several technical interviews, including a live HackerRank interview with a problem that was probably a LeetCode medium on a tree, followed by an onsite.
Candidate reports say interviewers care about how you approach a problem and explain your thinking. A London report advises being quick and correct. An experienced London candidate rejected after a one-hour coding round blamed a poor first choice of data structure and not talking through their thinking while coding.
Jane Street's published example question starts simple and is extended in stages. A guide for mid- and senior-level engineers describes practical, underspecified onsite problems, and a senior candidate describes long, collaborative coding rounds.
Guides disagree on the loop shape. One, written for mid- and senior-level engineers, describes a recruiter call, a one-hour phone screen and a five-hour onsite that includes a project deep dive. Another describes online assessments, one or two live sessions, then an onsite of three to four rounds of about 70 minutes. Neither is first-hand.
Jane Street says candidates usually hear back within a week. Students who are turned down are asked to wait at least a year before reapplying. One rejected candidate was told that feedback isn't part of the process.
Jane Street considers each application for all open roles globally. Its own postings list full-time new-grad software engineer roles in New York and Singapore, and aggregators repost openings in London and Hong Kong.
A repost of a Jane Street New York software engineer opening says the firm doesn't expect candidates to know functional programming, OCaml, Python or finance.
A London report (September 2025, level not stated) describes one phone screen and four onsite rounds: two coding, one system design and one presentation. The same aggregator shows a 15% success rate from 13 London experiences, a small sample.
One guide says software engineers face less intense probability questions than trader candidates. One Glassdoor review of unknown role mentions an expected-value question.
Jane Street says it has no GPA or degree requirement, and that its internships have no real requirements.

Likely · 1

Entry-level candidates should expect collaborative coding at about LeetCode-medium level that grows with added requirements, and little or no puzzle or math work. The official pages and the new-grad report support this.