# Engineer
**Role:** Software Engineer · **Level:** L3
**Company:** [Instacart](https://scaleengineer.com/companies/instacart)
**Difficulty:** Medium
**Salary:** US$100000 - US$130000
**Experience:** 1 - 3
**Timeline:** ~14 days
Instacart's Software Engineer L3 interview process is designed to assess a candidate's foundational technical skills, problem-solving abilities, and cultural fit within the company. The process typically involves multiple rounds, starting with an initial screening and progressing through technical interviews and a final hiring manager discussion.
Canonical: https://scaleengineer.com/interviews/instacart/l3-software-engineer
---
## Overall evaluation

- Technical Skills
- Communication
- Behavioral and Cultural Fit

## Questions asked

- Write a function to reverse a linked list.
- Given an array of integers, find the two numbers that add up to a specific target.
- Explain the difference between a process and a thread.
- How would you design a URL shortener?
- Tell me about a time you disagreed with a teammate and how you resolved it.
- What are your strengths and weaknesses?
- Describe a situation where you had to deal with ambiguity.

## Preparation tips

### lists

- Review fundamental data structures (arrays, linked lists, trees, graphs, hash maps) and algorithms (sorting, searching, dynamic programming, recursion).
- Practice coding problems on platforms like LeetCode, HackerRank, or Coderbyte, focusing on medium-difficulty problems.
- Understand basic system design concepts, such as scalability, availability, and trade-offs.
- Prepare to discuss your past projects in detail, focusing on your contributions and the challenges you faced.
- Research Instacart's products, mission, and values to tailor your answers.
- Practice behavioral questions using the STAR method (Situation, Task, Action, Result).
- Be ready to explain your thought process clearly and concisely during coding exercises.

### studyPlan

- {"title":"Data Structures and Algorithms Fundamentals","longDescription":"Weeks 1-2: Focus on core data structures like arrays, linked lists, stacks, queues, trees (binary trees, BSTs, heaps), and hash tables. Practice problems related to these structures, emphasizing time and space complexity analysis. Cover basic algorithms like sorting (quicksort, mergesort), searching (binary search), and recursion.","shortDescription":"Weeks 1-2: Data Structures (Arrays, Lists, Trees, HashMaps) & Basic Algorithms (Sorting, Searching, Recursion)."}
- {"title":"Algorithms and System Design Basics","longDescription":"Weeks 3-4: Dive into more advanced algorithms such as dynamic programming, graph traversal (BFS, DFS), and greedy algorithms. Practice problems that require combining multiple data structures and algorithms. Begin exploring introductory system design concepts like API design, database choices, and caching.","shortDescription":"Weeks 3-4: Advanced Algorithms (DP, Graphs) & Intro System Design."}
- {"title":"Behavioral Preparation and Company Research","longDescription":"Week 5: Focus on behavioral questions. Prepare stories using the STAR method for common themes like teamwork, problem-solving, handling failure, and leadership. Research Instacart's company culture and values to align your responses. Practice explaining your resume projects in detail.","shortDescription":"Week 5: Behavioral Questions (STAR method) & Company Research."}
- {"title":"Mock Interviews and Final Review","longDescription":"Week 6: Mock interviews. Practice coding problems under timed conditions and simulate the interview environment. Get feedback on your communication, problem-solving approach, and coding style. Review any areas where you felt weak during practice.","shortDescription":"Week 6: Mock Interviews & Final Review."}

## Location differences

- {"location":"Remote","differences":{"tips":["Research Instacart's presence and operations in this specific region.","Be prepared to discuss how your skills align with local team needs.","Highlight any experience working with diverse or international teams."],"interviewFocus":["Adaptability to different work environments.","Communication skills in a diverse team.","Understanding of local market trends (if applicable to the role)."],"commonQuestions":["Tell me about a challenging project you worked on at your previous company.","How do you handle conflicting priorities?","Describe a time you had to learn a new technology quickly."]}}
- {"location":"On-site (e.g., San Francisco, Toronto)","differences":{"tips":["Familiarize yourself with the specific technologies commonly used by Instacart's engineering teams in this location.","Prepare examples of successful in-person collaboration.","Show enthusiasm for Instacart's mission and its impact on the local community."],"interviewFocus":["Teamwork and collaboration within a co-located environment.","Understanding of Instacart's on-site engineering practices.","Alignment with the company's core values and office culture."],"commonQuestions":["Describe your experience with our specific tech stack used in this office.","How do you collaborate with cross-functional teams in a physical office setting?","What are your thoughts on our office culture and how do you see yourself contributing?"]}}

## Round 1: Coding Challenge
**Type:** Technical Interview - Coding · **Difficulty:** Medium · **Duration:** 45 min
Coding exercise to assess problem-solving and implementation skills.
This round typically involves a coding exercise, often conducted via a shared online editor. The interviewer will present a problem, and you'll be expected to write code to solve it. They will assess your ability to understand the problem, choose appropriate data structures and algorithms, write clean and efficient code, and test your solution thoroughly. Expect to explain your approach and justify your choices.
**Interviewers look for:** A candidate who can translate a problem into working code.; Someone who can think critically about their solution.; A candidate who communicates their thought process effectively.
**Evaluation criteria:** Correctness of the solution; Efficiency of the solution (time and space complexity); Code clarity and readability; Ability to handle edge cases; Problem-solving approach
**Common rejection reasons:** Inability to articulate thought process.; Poor coding practices (e.g., unreadable code, lack of comments).; Failure to consider edge cases.; Difficulty in debugging code.
## Questions

- Given a binary tree, find its inorder traversal.
- Implement a function to find the kth smallest element in an unsorted array.

## Preparation tips

- Practice coding on platforms like LeetCode, HackerRank, or Coderbyte.
- Focus on understanding time and space complexity (Big O notation).
- Write clean, well-commented code.
- Think out loud and explain your thought process to the interviewer.
- Don't be afraid to ask clarifying questions.

## Round 2: System Design
**Type:** Technical Interview - System Design · **Difficulty:** Medium · **Duration:** 60 min
Design a scalable system and discuss trade-offs.
This round focuses on your ability to design scalable and robust systems. You'll be given a high-level problem (e.g., design a social media feed, a URL shortener, or an e-commerce checkout system) and asked to propose a solution. The interviewer will probe your design choices, asking about data storage, APIs, caching, load balancing, and potential bottlenecks. The focus is on your thought process and ability to handle trade-offs, not necessarily on a perfect, fully detailed solution.
**Interviewers look for:** A candidate who can think about distributed systems and scalability.; Someone who can make reasoned design choices.; A candidate who can communicate complex ideas clearly.
**Evaluation criteria:** Scalability of the proposed solution; Availability and reliability considerations; Choice of appropriate technologies and data stores; Understanding of trade-offs; Ability to break down a complex problem
**Common rejection reasons:** Lack of understanding of fundamental system design principles.; Inability to discuss trade-offs and justify design decisions.; Overly complex or simplistic solutions.; Poor communication of design ideas.
## Questions

- Design a system to handle real-time notifications for a messaging app.
- How would you design a rate limiter for an API?

## Preparation tips

- Study common system design patterns and concepts.
- Understand trade-offs between different technologies (e.g., SQL vs. NoSQL, REST vs. GraphQL).
- Practice designing common systems like Twitter, Instagram, or Uber.
- Be prepared to discuss scalability, availability, and performance.
- Clearly articulate your design choices and the reasoning behind them.

## Round 3: Behavioral and Fit Interview
**Type:** Behavioral Interview · **Difficulty:** Medium · **Duration:** 45 min
Assess behavioral competencies and cultural fit.
This round assesses your behavioral competencies and cultural fit. You'll be asked questions about your past experiences, focusing on how you've handled various situations (e.g., challenges, conflicts, successes). The interviewer wants to understand your work style, how you collaborate with others, and whether you align with Instacart's core values. Use the STAR method (Situation, Task, Action, Result) to structure your answers.
**Interviewers look for:** A candidate who is a good cultural fit.; Someone who can demonstrate collaboration and teamwork.; A candidate who is motivated and passionate about Instacart's mission.
**Evaluation criteria:** Alignment with Instacart's values; Teamwork and collaboration skills; Problem-solving approach in past situations; Self-awareness and ability to learn from experiences; Communication and interpersonal skills
**Common rejection reasons:** Lack of self-awareness.; Inability to provide specific examples.; Poor communication of past experiences.; Mismatch with company values or team dynamics.; Negative attitude or lack of enthusiasm.
## Questions

- Tell me about a time you failed and what you learned from it.
- Describe a situation where you had to work with a difficult colleague.
- Why are you interested in Instacart?

## Preparation tips

- Review Instacart's mission, vision, and values.
- Prepare specific examples using the STAR method for common behavioral questions.
- Be ready to discuss your career goals and why you're interested in Instacart.
- Show enthusiasm and a positive attitude.
- Ask thoughtful questions about the team and company culture.