# Software Engineer
**Role:** Software Engineer · **Level:** L2
**Company:** [Jane Street](https://scaleengineer.com/companies/jane-street)
**Difficulty:** Hard
**Salary:** US$110000 - US$150000
**Experience:** 2 - 5
**Timeline:** ~14 days
The Software Engineer interview at Jane Street for an L2 level position is a rigorous process designed to assess a candidate's technical proficiency, problem-solving abilities, and cultural fit within the firm. It typically involves multiple rounds, including technical interviews focusing on data structures, algorithms, and system design, as well as behavioral interviews to gauge teamwork and communication skills. The goal is to identify candidates who can contribute effectively to the firm's trading and technology initiatives.
Canonical: https://scaleengineer.com/interviews/jane-street/l2-software-engineer
---
## Overall evaluation

- Technical Proficiency
- Problem Solving & Design
- Cultural Fit & Motivation

## Questions asked

- Given an array of integers, find the contiguous subarray with the largest sum.
- Design a rate limiter.
- Explain the difference between a process and a thread.
- Tell me about a time you failed and what you learned from it.
- How would you optimize a slow database query?
- Implement a function to reverse a linked list.
- Describe the CAP theorem and its implications for distributed systems.
- What are your strengths and weaknesses?
- How would you design a system to handle real-time notifications for a social media platform?
- Write a function to find the k-th smallest element in an unsorted array.

## Preparation tips

### lists

- Master fundamental data structures (arrays, linked lists, trees, graphs, hash tables) and algorithms (sorting, searching, dynamic programming, graph traversal).
- Practice coding problems on platforms like LeetCode, HackerRank, and AlgoExpert, focusing on medium to hard difficulty.
- Study system design principles, including scalability, reliability, and performance optimization.
- Review common behavioral interview questions and prepare STAR method (Situation, Task, Action, Result) responses.
- Understand the basics of financial markets and trading if interviewing for a trading-related role.
- Research Jane Street's culture, values, and recent projects.
- Prepare thoughtful questions to ask the interviewers.

### studyPlan

- {"title":"Data Structures Fundamentals","longDescription":"Weeks 1-2: Focus on core data structures like arrays, linked lists, stacks, queues, hash tables, trees (binary trees, BSTs, heaps), and graphs. Practice implementing them and understanding their time and space complexities. Solve problems related to these structures.","shortDescription":"Weeks 1-2: Data Structures (Arrays, Lists, Trees, Graphs, Hash Tables). Practice implementations and basic problems."}
- {"title":"Algorithm Mastery","longDescription":"Weeks 3-4: Dive deep into algorithms, including sorting (quicksort, mergesort), searching (binary search), dynamic programming, greedy algorithms, graph algorithms (BFS, DFS, Dijkstra's), and recursion. Solve a variety of problems for each category.","shortDescription":"Weeks 3-4: Algorithms (Sorting, Searching, DP, Greedy, Graphs). Solve diverse problems."}
- {"title":"System Design Introduction","longDescription":"Week 5: Begin system design. Study concepts like load balancing, caching, databases (SQL vs. NoSQL), message queues, microservices, and distributed systems. Practice designing common systems like Twitter's feed or a URL shortener.","shortDescription":"Week 5: System Design basics (Scalability, Caching, Databases, Distributed Systems). Practice designing systems."}
- {"title":"Behavioral Preparation","longDescription":"Week 6: Focus on behavioral preparation. Identify key experiences from your resume that demonstrate teamwork, leadership, problem-solving, and handling challenges. Prepare STAR method answers for common behavioral questions.","shortDescription":"Week 6: Behavioral Interview prep. Prepare STAR method answers for common questions."}
- {"title":"Mock Interviews & Feedback","longDescription":"Week 7: Mock interviews. Conduct mock interviews with peers or mentors, focusing on both technical and behavioral aspects. Get feedback on your communication, problem-solving approach, and overall presentation.","shortDescription":"Week 7: Mock Interviews (Technical & Behavioral). Seek feedback."}
- {"title":"Final Review & Refinement","longDescription":"Week 8: Review and refine. Go over weak areas identified during mock interviews. Revisit challenging problems and system design concepts. Ensure you have a solid understanding of the fundamentals and are ready to articulate your thoughts clearly.","shortDescription":"Week 8: Review weak areas, revisit problems and concepts. Final preparation."}

## Location differences

- {"location":"New York","differences":{"tips":["Familiarize yourself with common trading strategies and financial instruments.","Be prepared to discuss your experience with high-performance computing and distributed systems.","Highlight any experience with C++, Java, or Python in a performance-critical context."],"interviewFocus":["Emphasis on low-latency systems and performance optimization.","Understanding of financial markets and trading concepts is a plus.","Adaptability to fast-paced, dynamic environments."],"commonQuestions":["Discuss a time you had to debug a complex system. What was your approach?","How would you design a system to handle real-time stock price updates for a large number of users?","Explain the trade-offs between different database technologies for a high-frequency trading application."]}}
- {"location":"London","differences":{"tips":["Review fundamental data structures and algorithms thoroughly.","Practice explaining your thought process clearly and concisely.","Be ready to discuss your contributions to past projects and your learning experiences."],"interviewFocus":["Strong focus on core computer science fundamentals.","Problem-solving and analytical skills are paramount.","Ability to work collaboratively in a team environment."],"commonQuestions":["Describe a challenging project you worked on and how you overcame obstacles.","How would you design a scalable caching system for a web application serving millions of users?","What are the key considerations when designing a distributed consensus algorithm?"]}}
- {"location":"Hong Kong","differences":{"tips":["Prepare examples that showcase your problem-solving and teamwork skills.","Brush up on your knowledge of distributed systems and big data technologies.","Demonstrate your enthusiasm for learning and adapting to new challenges."],"interviewFocus":["Emphasis on system design and scalability.","Understanding of data processing and analysis techniques.","Cultural fit and ability to thrive in a collaborative environment."],"commonQuestions":["Tell me about a time you disagreed with a teammate. How did you handle it?","How would you design a system to process and analyze large volumes of historical market data?","What are the challenges of building a fault-tolerant distributed system?"]}}

## Round 0: HR Screen
**Type:** HR / Recruiter Screen · **Difficulty:** Easy · **Duration:** 15 min
Initial screening to assess interest and basic qualifications.
This is typically the first or last touchpoint with the recruiting team. They will discuss the role in more detail, answer any logistical questions you may have, and assess your overall interest and fit for the company. This is also an opportunity for them to gauge your understanding of the role and your career aspirations.
**Interviewers look for:** Genuine interest in the role and company.; Good communication and engagement.; Alignment with team's work and culture.; Professionalism.
**Evaluation criteria:** Candidate's interest and enthusiasm.; Alignment with team and company culture.; Clarification of any remaining questions.; Logistics and expectations.
**Common rejection reasons:** Lack of enthusiasm for the role or company.; Unrealistic salary expectations.; Poor fit with the team's dynamics.; Failure to ask insightful questions.
## Questions

- What are your salary expectations?
- Do you have any questions for me about the role or the company?
- What are you looking for in your next role?

## Preparation tips

- Be prepared to talk about your resume and why you applied.
- Have questions ready about the role, team, or company culture.
- Express your enthusiasm for the opportunity.
- Be professional and courteous.

## Round 1: Technical Coding Round 1
**Type:** Data Structures and Algorithms Interview · **Difficulty:** Hard · **Duration:** 45 min
Tests fundamental data structures and algorithms through coding problems.
This round focuses on your core computer science knowledge. You will be asked to solve coding problems that test your understanding of data structures (e.g., arrays, linked lists, trees, graphs, hash maps) and algorithms (e.g., sorting, searching, dynamic programming, recursion). The interviewer will assess not only if you can arrive at a correct solution but also how you approach the problem, communicate your thought process, and consider edge cases and efficiency.
**Interviewers look for:** Strong grasp of data structures and algorithms.; Clean and efficient coding style.; Logical problem-solving approach.; Ability to explain trade-offs.
**Evaluation criteria:** Correctness of code.; Efficiency of algorithms (time and space complexity).; Clarity of thought process and communication.; Ability to handle edge cases.
**Common rejection reasons:** Inability to articulate thought process.; Incorrect or inefficient solutions to coding problems.; Lack of understanding of fundamental data structures and algorithms.
## Questions

- Given a binary tree, find its inorder traversal.
- Implement a function to find the median of a stream of numbers.
- Find the length of the longest substring without repeating characters.

## Preparation tips

- Practice coding problems on platforms like LeetCode, focusing on medium to hard difficulty.
- Understand the time and space complexity of your solutions.
- Be prepared to write code on a whiteboard or in a shared editor.
- Think out loud and explain your approach before coding.

## Round 2: System Design Round
**Type:** System Design Interview · **Difficulty:** Hard · **Duration:** 60 min
Evaluates ability to design scalable and reliable systems.
This round assesses your ability to design complex, scalable, and reliable systems. You'll be presented with a high-level problem (e.g., design a URL shortener, a social media feed, or a distributed cache) and expected to discuss various aspects of the design, including data storage, APIs, scalability, performance, and potential bottlenecks. The focus is on your thought process and ability to make informed design decisions.
**Interviewers look for:** System design thinking.; Knowledge of distributed systems principles.; Ability to break down complex problems.; Pragmatic approach to design choices.
**Evaluation criteria:** Scalability of the proposed design.; Reliability and fault tolerance.; Understanding of trade-offs between different design choices.; Ability to handle large amounts of data and traffic.; Clarity and structure of the design explanation.
**Common rejection reasons:** Inability to design scalable and robust systems.; Poor understanding of distributed systems concepts.; Lack of consideration for trade-offs and failure scenarios.
## Questions

- Design a system like Twitter's news feed.
- How would you design a distributed key-value store?
- Design a rate limiter for an API.

## Preparation tips

- Study common system design patterns and architectures.
- Understand concepts like load balancing, caching, databases (SQL vs. NoSQL), message queues, and distributed consensus.
- Practice designing systems by breaking them down into components.
- Be prepared to discuss trade-offs and justify your design choices.

## Round 3: Behavioral / Managerial Round
**Type:** Behavioral Interview · **Difficulty:** Medium · **Duration:** 30 min
Assesses soft skills, teamwork, and cultural fit.
This round focuses on your behavioral and soft skills. You'll be asked questions about your past experiences, how you handle challenges, work in teams, and your motivations for joining Jane Street. The goal is to understand your personality, work ethic, and how well you would fit into the company culture. Use the STAR method (Situation, Task, Action, Result) to structure your answers.
**Interviewers look for:** Team player mentality.; Effective communication.; Problem-solving skills beyond coding.; Enthusiasm and motivation.; Cultural alignment.
**Evaluation criteria:** Communication and interpersonal skills.; Teamwork and collaboration abilities.; Problem-solving approach in non-technical contexts.; Self-awareness and ability to reflect on past experiences.; Cultural fit with Jane Street's values.
**Common rejection reasons:** Poor communication skills.; Lack of collaboration or teamwork.; Negative attitude or lack of enthusiasm.; Inability to provide specific examples of past experiences.
## Questions

- Tell me about a time you had to work with a difficult colleague.
- Describe a project where you faced a significant technical challenge and how you overcame it.
- Why are you interested in working at Jane Street?

## Preparation tips

- Prepare specific examples from your past experiences using the STAR method.
- Think about situations where you demonstrated teamwork, leadership, problem-solving, and resilience.
- Be ready to discuss your career goals and why you are interested in Jane Street.
- Be honest and authentic in your responses.