Jane Street Software Engineer Interview Guide

tl;dr

Jane Street is “solving the puzzle of global markets” through their trading firm, and they’ve built a small but mighty team of technologists and trading specialists to fuel their work toward this mission.

As a tight-knit company of just 2,600 people, Jane Street prioritizes collaboration and face-to-face engagement above all else, with most employees working from their New York City headquarters. The company is always looking to add more software engineers to the mix to help build out their software, most of which is created in-house.

The firm is a well-oiled machine that champions its talent as much as its trading tech. You might think that makes for a cut-and-dry hiring process, but Jane Street’s hiring practices are pretty unassuming. They focus more on who their candidates are and what they’re like to work with than which boxes they tick on a checklist. In fact, their software engineering job descriptions don’t quantify your experience in years or in terms of which programming languages you know; instead, they simply ask that you have “deep experience with—and love for—technology.”

While the company emphasizes the behavioral aspect of hiring, make no mistake: they take the interview process seriously, and they’re invested in making sure they hire the best people for their team. They’re unassuming, but they’re not unstructured.

If you’re selected for an interview, you’ll dive right into the deep end of Jane Street’s two-part hiring process, which consists of a technical screen and then a full day on-site. The best way to ace a Jane Street interview is to know what you know and communicate effectively. They’re not looking for people who have all the answers or know how to code in OCaml—they’re looking for people who communicate well and know how to work with others to find the best solution.

There are a few things that separate a Jane Street interview from other tech interviews:

1. Jane Street hiring lore: Some people say the company’s software engineering interviews are chock full of brain teasers and mathematical questions, but Jane Street recruiters and prep materials dispel this idea. Recent candidates confirmed they’ve had a more laid-back, collaborative (albeit still challenging) experience.
2. Two interviewers per round: The on-site is split into three coding rounds and one behavioral round, each with two interviewers. Don’t worry, it’s not an intimidation tactic—Jane Street says this is so one interviewer can focus on note-taking while the other is asking questions. If anything, using this many resources for hiring shows their commitment to their hiring processes.
3. Unique coding rounds: The coding rounds themselves are non-standard, with each round lasting 70 minutes and asking questions you probably won’t see during any other tech interview.

Compensation

Jane Street is one of the highest paying companies in tech. Full stop. New grads can make $350K-$450K. That's unheard of. Packages near and over $1,000,000 might be more common here than at any other tech company. Plus, they bias towards cash which is unique. And allegedly, since they're a trading firm, employees can invest in their proprietary high-performing funds.

What does a Jane Street Software Engineer do?

Jane Street Software Engineers build and advance the company’s technical infrastructure. Since they’re a small team, there’s plenty of opportunity to make big, impactful contributions. According to Jane Street’s Technology page, their software handles billions of dollars in transactions daily.

The kind of work you do will really depend on which team you land on, but in general, you can expect to:

• Perform functional programming and development using OCaml
• Implement systems automations, network monitoring, and risk models
• Perform data analysis and visualization using Python
• Contribute regularly to open-source projects

The company knows that good work doesn’t happen in a vacuum, so they highly encourage software engineers to lean on teammates for help when they need it. This is why collaboration is such an important component of their interview process—they want to make sure you’re 1) good to work with in a general sense, and 2) someone who isn’t afraid to ask questions or ask for help.

Before you apply

1. Take a look at Jane Street’s interview prep resources.
2. Review Jane Street’s general interview guide and their software engineering interview blog.
3. Prep for your interview with Exponent’s Software Engineering Interviews course.
4. Check out some of the top interview questions software engineers are asked during interviews.

Interview process

Every detail of the interview process at Jane Street is carefully orchestrated yet surprisingly flexible. Most companies interview to fill roles in specific domains at specific levels, but things are more lax at Jane Street. Instead, you’ll go through the interview process without knowing which team you might work for or what level your role might be. This gives the company flexibility to match you with the role and team you’re the best fit for at the end of the interview cycle.

The software engineering interview process is split into two parts:

1. A remote technical screen with a coding assessment
2. An on-site final round with four hands-on coding assessments

1. Technical screen

Jane Street cuts through the hum-drum of standard SWE hiring processes by eliminating the recruiter screen and having candidates dive straight into the technical screen. This is a 60-minute round conducted virtually and it gives you a complex problem that’s not a typical LeetCode question.

One of the challenges in preparing for a Jane Street interview is that they almost want you to be unprepared. Interviewers are looking to see how you use your existing technical toolkit and communication skills to approach a new problem, so their goal is to give you a problem you haven’t seen before.

The best way to prepare for this round is to spend some time studying the programming language you’re most familiar with. The team expects you to code—not pseudo-code—throughout the entire interview process, so being prepared to use the language you know best will let you showcase your full SWE abilities.

In addition to your programming language of choice, here are some topics to study for this round (and the final round):

• Data structures and algorithms
• Object-oriented programming
• Arrays and hash maps

2. Final round (on-site)

The final on-site round is made up of:

• Four 70-minute coding assessments
• One potential behavioral round that deep dives into a technical project you worked on

During the coding assessments, you’re encouraged to do work in the way that feels most natural to you—using your own laptop and equipment, if possible, and using the programming language you’re most familiar with.

This process sounds highly technical at first glance, but don’t be fooled—the behavioral aspect is just as important to your success, and it’ll be at play even during the coding rounds.

Interviewers aren’t just looking to see whether you can find the right answers (although yes, they do like clean solutions); they’re assessing whether you’re someone they’d actually enjoy working with.

The on-site is a full-day event, so you can expect two coding rounds before lunch and two coding rounds after. During these rounds, you’ll have 60 minutes to work on your solution and 10 minutes at the end for Q&A.

Like the technical screen, the on-site is a highly collaborative effort, with interviewers actively engaging with you as you work through your solutions. They’ll offer hints or ask leading questions if they see you’re getting stuck, and they’ll expect you to ask them clarifying questions along the way. They might even give you a solution if you need it, just to keep things moving. This isn’t a bad sign—asking questions and accepting hints is more important to Jane Street than seeing your ability to find solutions on your own.

Topics to study for this round include:

• Merkle Tree
• Hash functions

Interview questions

Coding

The coding questions are multipart and really open-ended, so there’s no one-size-fits-all solution. It’s totally normal for candidates to not finish their solution, so don’t get anxious about that. Your goal is strictly to show Jane Street how you work and what your thought process looks like. As the final round progresses, you’ll build on your solutions from the previous round.

One of the most unique aspects of a Jane Street Software Engineering interview is their coding questions. These are complex questions that you’re not likely to see anywhere else, and this is by design—they want to see how you approach a problem you’ve never seen before, and they don’t want you to be too rehearsed in your problem-solving. Jane Street SWE candidates have seen questions like:

• Write a memoized version of function f (i.e., a function g of the same type) that returns the values g(x) = f(x) for all x, while only performing expensive computations once for each input value.
• Implement a game like Connect Four by writing a game state class.
• Implement a tree class and a hash function for each node.

Behavioral

Typically reserved for senior-level roles, the final on-site round is a deep dive into a past project you worked on, and this is where a lot of the behavioral questions come into play. This interview is more conversational in nature; you’ll steer the discussion, but your interviewers will be active participants. You’ll discuss a technical project that really challenged you, answering these questions:

• What problem were you solving?
• What made it difficult and what challenges did you face along the way?
• How did you approach your solution and any implementations? What did decision-making look like throughout the project?

Expect your interviewers to really drill into the specifics of why you made each decision, what the outcome was, and what you might have done differently. Some candidates have had a follow-up question like:

• How would you design your solution differently if concurrency was a concern?

To prepare for this round, you can have an idea of a few projects you’d like to discuss, the motivations behind them, and their overall impact. But again, don’t do too much background prep—if interviewers sense you’re too rehearsed, they’ll ask you to discuss a different project.

Some candidates mentioned that interviewers asked them about systems they hadn’t directly worked on, so this is a little bit of a “gotcha” from Jane Street. They want to see how well you know the systems outside of what you work on day-to-day. Since they’re such a small team, you might be expected to jump in and help cross-functional SWE teammates when you can, so be ready to show you’re prepared for that.

Additional resources

• Look through Jane Street’s sample question walkthrough.
• Learn more about what to expect from a Jane Street interview.
• Practice a few coding questions (even if you won’t see them during your interview).

FAQs about the Jane Street SWE interview

How should I prepare for a Jane Street Software Engineer interview?

As counterintuitive as it might sound, in some ways, the best way to prepare for a Jane Street Software Engineer interview is to not prepare (at least not too much).

Feel free to brush up on your favorite programming language, data structures and algorithms, and some past projects you’d like to highlight. But make sure you’re still able to showcase your skills and experience in a way that’s natural and honest, because that’s the experience Jane Street is evaluating you on.

With that said, you should be ready to ask clarifying questions throughout the interview rounds and expect a lot of “Why did you do X instead of X?” follow-up questions from the team. Honing your communication skills is what’ll set you apart during the interview process.

How much do Jane Street Software Engineers make?

If you look around the web, there are varying salary ranges for Jane Street Software Engineers. In general, Jane Street is one of the best paying companies in tech. Packages range from $300K to above $1,000,000, and are skewed towards cash (which is very rare for the industry.)

How long is the Jane Street Software Engineer interview process?

Jane Street tries to get back to candidates as quickly as possible, so you should hear from them within a few days of each interview round. In total, the interview process typically takes 3–4 weeks.