# Engineer 2
**Role:** Software Engineer · **Level:** L4
**Company:** [Instacart](https://scaleengineer.com/companies/instacart)
**Difficulty:** Medium to Hard
**Salary:** US$120000 - US$160000
**Experience:** 3 - 7
**Timeline:** ~14 days
Instacart's Software Engineer (L4) interview process is designed to assess a candidate's technical proficiency, problem-solving abilities, and cultural fit within the company. The process typically involves multiple rounds, including technical interviews focusing on data structures, algorithms, and system design, as well as behavioral interviews to gauge collaboration and communication skills.
Canonical: https://scaleengineer.com/interviews/instacart/l4-software-engineer
---
## Overall evaluation

- Technical Skills
- Behavioral and Cultural Fit

## Questions asked

- Given a list of grocery items and their prices, design a system to calculate the total cost of a shopping cart, considering discounts and taxes.
- How would you design a recommendation engine for Instacart's customers?
- Explain the difference between concurrency and parallelism and provide examples.
- Describe a situation where you had to mentor a junior engineer. What was your approach?
- Write a function to find the k-th largest element in an unsorted array.
- How would you design a distributed cache for Instacart's product catalog?
- Tell me about a time you disagreed with a technical decision. What did you do?
- What are the trade-offs of using microservices versus a monolithic architecture?
- Implement a function to validate if a binary tree is a Binary Search Tree.
- How would you handle scaling issues if Instacart experienced a sudden surge in user traffic?

## Preparation tips

### lists

- Review fundamental data structures (arrays, linked lists, trees, graphs, hash maps) and algorithms (sorting, searching, dynamic programming, graph traversal).
- Practice coding problems on platforms like LeetCode, HackerRank, or Coderbyte, focusing on medium to hard difficulty.
- Study system design principles, including scalability, availability, reliability, and common architectural patterns (microservices, load balancing, caching, databases).
- Prepare for behavioral questions by reflecting on your past experiences using the STAR method (Situation, Task, Action, Result).
- Understand Instacart's business model, products, and challenges to tailor your answers and demonstrate interest.
- Research common interview questions for Software Engineer roles at Instacart and similar tech companies.

### studyPlan

- {"title":"Data Structures and Algorithms","longDescription":"Weeks 1-2: Focus on core data structures and algorithms. Cover arrays, linked lists, stacks, queues, trees (binary search trees, AVL trees, heaps), graphs, and hash tables. Practice algorithms like sorting (quicksort, mergesort), searching (binary search), recursion, dynamic programming, and graph traversal (BFS, DFS). Aim to solve at least 2-3 problems per day.","shortDescription":"Weeks 1-2: Data Structures & Algorithms fundamentals. Solve 2-3 problems daily."}
- {"title":"System Design","longDescription":"Weeks 3-4: Dive into system design. Understand concepts like API design, load balancing, caching strategies, database choices (SQL vs. NoSQL), message queues, and distributed systems. Practice designing common systems like a URL shortener, a Twitter feed, or an e-commerce platform. Focus on trade-offs and scalability.","shortDescription":"Weeks 3-4: System Design principles. Practice designing common systems."}
- {"title":"Behavioral Preparation","longDescription":"Week 5: Prepare for behavioral interviews. Identify key projects and experiences that demonstrate leadership, teamwork, problem-solving, and handling challenges. Use the STAR method to structure your answers. Prepare specific examples related to Instacart's values.","shortDescription":"Week 5: Behavioral preparation using STAR method. Align with Instacart's values."}
- {"title":"Mock Interviews and Review","longDescription":"Week 6: Mock interviews and review. Conduct mock interviews with peers or mentors to simulate the actual interview environment. Review your weak areas based on feedback and practice coding and system design problems under timed conditions.","shortDescription":"Week 6: Mock interviews and review weak areas."}

## Location differences

- {"location":"North America","differences":{"tips":["Familiarize yourself with common distributed system patterns and their applications at scale.","Be prepared to discuss your experience with cloud platforms and microservices architecture.","Practice articulating your thought process clearly and concisely, especially when discussing trade-offs."],"interviewFocus":["Candidates in North America are often evaluated on their ability to scale systems and handle large datasets, given the market size.","Emphasis on practical application of distributed systems concepts and cloud technologies (AWS, GCP).","Behavioral questions may lean towards collaboration in a fast-paced, growth-oriented environment."],"commonQuestions":["How would you design a system to handle real-time grocery order updates for shoppers and customers?","Discuss a time you had to deal with a difficult stakeholder. How did you manage the situation?","Explain the trade-offs between using a relational database versus a NoSQL database for our product catalog."]}}
- {"location":"Europe","differences":{"tips":["Review best practices for secure coding and data handling.","Be ready to discuss your approach to testing and code reviews.","Highlight instances where you've demonstrated resilience and adaptability."],"interviewFocus":["Candidates in Europe might be assessed on their understanding of data privacy regulations (e.g., GDPR) and its impact on system design.","Focus on robust software development practices and code quality.","Behavioral questions may explore adaptability and problem-solving in diverse team settings."],"commonQuestions":["Describe a challenging bug you encountered and how you debugged it.","How would you optimize a query that is performing poorly?","Tell me about a project where you had to work with ambiguous requirements."]}}

## Round 1: Coding Challenge
**Type:** Technical Interview (Coding) · **Difficulty:** Medium · **Duration:** 45 min
Solve 1-2 coding problems focusing on data structures and algorithms.
This round focuses on your fundamental programming skills. You will be asked to solve one or two coding problems, typically involving data structures and algorithms. The interviewer will assess your ability to understand the problem, devise a solution, write clean code, and analyze its time and space complexity. Expect to be asked follow-up questions to explore alternative approaches or edge cases.
**Interviewers look for:** A candidate who can break down a problem into smaller, manageable parts.; Someone who can identify and apply appropriate data structures and algorithms.; A coder who writes clean, efficient, and well-tested code.
**Evaluation criteria:** Correctness of the solution; Efficiency of the solution (time and space complexity); Code clarity and readability; Problem-solving approach
**Common rejection reasons:** Inability to articulate thought process clearly.; Lack of fundamental data structures and algorithms knowledge.; Poor coding practices (e.g., inefficient solutions, lack of error handling).
## Questions

- Given an array of integers, find the contiguous subarray with the largest sum.
- Implement a function to reverse a linked list.
- Find the first non-repeating character in a string.

## Preparation tips

- Practice coding problems on platforms like LeetCode, focusing on medium difficulty.
- Be comfortable explaining your thought process out loud.
- Write code on a whiteboard or in a shared editor, simulating the interview environment.
- Test your code with various edge cases.

## Round 2: System Design
**Type:** System Design Interview · **Difficulty:** Hard · **Duration:** 60 min
Design a scalable system, discussing components, trade-offs, and scalability.
This round assesses your ability to design complex, scalable, and reliable systems. You'll be given an open-ended problem, such as designing a service like Twitter's feed or a ride-sharing platform. The interviewer will expect you to discuss requirements, propose a high-level design, dive into specific components (databases, APIs, caching), and consider aspects like scalability, availability, and trade-offs. You should be prepared to draw diagrams and explain your reasoning.
**Interviewers look for:** A candidate who can think about systems at a high level.; Someone who understands distributed systems principles.; An individual who can identify potential bottlenecks and failure points.; A candidate who can articulate design choices and justify them.
**Evaluation criteria:** System design approach; Scalability and performance considerations; Reliability and fault tolerance; Trade-off analysis; Clarity of explanation
**Common rejection reasons:** Inability to design scalable and reliable systems.; Lack of understanding of distributed systems concepts.; Poor consideration of trade-offs and failure scenarios.
## Questions

- Design a URL shortening service like Bitly.
- Design a system to track real-time user activity on a website.
- Design an API rate limiter.

## Preparation tips

- Study common system design patterns and architectures.
- Practice designing various systems, focusing on scalability and trade-offs.
- Understand concepts like CAP theorem, eventual consistency, and different database types.
- Be prepared to discuss your experience with cloud platforms (AWS, GCP, Azure).

## Round 3: Behavioral and Cultural Fit
**Type:** Behavioral Interview · **Difficulty:** Medium · **Duration:** 45 min
Discuss past experiences using STAR method, focusing on teamwork, leadership, and cultural fit.
This round focuses on your past experiences and how they align with Instacart's culture and values. You'll be asked behavioral questions that require you to provide specific examples using the STAR method. Topics may include teamwork, conflict resolution, handling failure, leadership, and dealing with ambiguity. The interviewer wants to understand how you operate in a team environment and your potential impact on the company culture.
**Interviewers look for:** A candidate who demonstrates Instacart's core values.; Someone who can communicate effectively and collaborate well.; An individual who takes ownership and drives results.; A candidate who is passionate about Instacart's mission.
**Evaluation criteria:** Behavioral competencies (teamwork, leadership, problem-solving); Communication skills; Cultural fit with Instacart; Motivation and career goals
**Common rejection reasons:** Lack of alignment with company values.; Poor communication or interpersonal skills.; Inability to provide specific examples of past behavior.; Lack of enthusiasm or interest in the role/company.
## Questions

- Tell me about a time you had to work with a difficult colleague. How did you handle it?
- Describe a project where you took initiative or demonstrated leadership.
- Tell me about a time you failed. What did you learn from it?
- Why are you interested in Instacart?

## Preparation tips

- Prepare stories using the STAR method for common behavioral questions.
- Research Instacart's mission, values, and culture.
- Think about how your experiences align with the specific role requirements.
- Be ready to ask thoughtful questions about the team and company.