Instacart Software Engineer Interview Questions + Guide in 2025

Instacart is a leading grocery delivery and pickup service that connects customers with their favorite local retailers.

As a Software Engineer at Instacart, you will be part of a dynamic team responsible for developing tools that facilitate the seamless running of production and staging services for software engineers, data scientists, and analysts. Your key responsibilities will include creating and maintaining infrastructure components, ensuring their security and availability, and collaborating closely with a small team that values ownership and accountability. The ideal candidate will possess a strong coding background, particularly in Python, along with a solid understanding of Linux server management and experience with cloud services like Amazon Web Services (AWS). Familiarity with configuration management tools, microservices architecture, and data analysis using SQL will further enhance your fit for this role.

Instacart values self-motivation and a sense of urgency, making it essential for candidates to demonstrate a proactive approach to problem-solving and a commitment to delivering high-quality solutions. This guide will help you prepare for your interview by providing insights into the role's expectations and the types of questions you may encounter, allowing you to approach the process with confidence and clarity.

The interview process for a Software Engineer at Instacart is structured to assess both technical skills and cultural fit within the team. It typically consists of several stages, each designed to evaluate different aspects of a candidate's qualifications and experience.

1. Initial Recruiter Screening

The process begins with a phone call from a recruiter, which usually lasts around 30 minutes. During this conversation, the recruiter will discuss your background, experience, and motivations for applying to Instacart. They may also cover basic topics such as your familiarity with the tech stack and your understanding of the role. This is an opportunity for you to ask questions about the company culture and the team dynamics.

2. Technical Phone Screen

Following the initial screening, candidates typically undergo a technical phone interview. This session usually lasts about 45-60 minutes and involves solving a coding problem, often using platforms like HackerRank. The questions may focus on data structures, algorithms, and coding challenges that reflect real-world scenarios. Candidates should be prepared to discuss their thought process and approach to problem-solving, as well as to demonstrate their coding skills in their language of choice.

3. Onsite Interview

The onsite interview is a more comprehensive evaluation, often lasting around 4-5 hours. It usually includes multiple rounds, such as two coding challenges, a system design interview, and a behavioral interview. The coding challenges may be structured in a multi-part format, where each part builds on the previous one. The system design interview assesses your ability to architect solutions and think critically about scalability and performance. The behavioral interview, often referred to as the "bar raiser" interview, focuses on your past experiences and how they align with Instacart's values and culture.

4. Final Discussions

After the onsite interviews, candidates may have follow-up discussions with team members or hiring managers. This stage is often less formal and allows for a deeper dive into the candidate's experiences and how they would fit within the team. It’s also a chance for candidates to ask more specific questions about the role and the company.

Throughout the process, candidates should be prepared for varying levels of engagement from interviewers, as experiences can differ significantly. It's essential to remain adaptable and proactive in seeking feedback and clarification during technical discussions.

Next, let's explore the specific interview questions that candidates have encountered during this process.

Here are some tips to help you excel in your interview.

Prepare for a Unique Interview Experience

Instacart's interview process can be quite different from what you might expect. Many candidates have reported that interviewers may not be fully engaged or may have distractions during the interview. To counter this, ensure you are well-prepared and can articulate your thought process clearly. Practice coding problems in a way that allows you to explain your reasoning as you go, as this can help keep the interviewer's attention and demonstrate your problem-solving skills.

Master the Technical Skills

Given that the role involves significant coding, focus on honing your skills in Python, AWS, and Linux. Review common data structures and algorithms, and practice coding problems on platforms like LeetCode or HackerRank. Be prepared for multi-part coding questions that build on each other, as this format has been noted in past interviews. Additionally, brush up on your knowledge of microservices and configuration management tools like Ansible or SaltStack, as these are relevant to the role.

Communicate Effectively

Since some interviewers may not provide much feedback during the coding portion, it’s crucial to communicate your thought process clearly. Don’t hesitate to ask clarifying questions if you’re unsure about the problem requirements. If you feel the interviewer is distracted, politely address it and refocus the conversation on your coding solution. This shows initiative and can help create a more engaging dialogue.

Be Ready for Behavioral Questions

Instacart values self-motivation and ownership, so be prepared to discuss your past experiences that demonstrate these qualities. Think of specific examples where you took the lead on a project or overcame challenges in a team setting. This will not only showcase your technical skills but also your fit within the company culture.

Manage Your Time Wisely

The onsite interview can be lengthy and mentally exhausting, often lasting several hours. Make sure to manage your time effectively during coding challenges, and don’t hesitate to ask for a break if you need one. If you find the interview format overwhelming, consider suggesting a split into multiple days, as some candidates have found this to be a more manageable approach.

Follow Up Professionally

After your interview, it’s a good practice to send a thank-you email to your recruiter or the interviewers. Express your appreciation for the opportunity and reiterate your interest in the position. This not only shows professionalism but also keeps you on their radar as they make their decisions.

By following these tips, you can navigate the interview process at Instacart with confidence and increase your chances of success. Good luck!

In this section, we’ll review the various interview questions that might be asked during a Software Engineer interview at Instacart. The interview process will likely focus on your coding skills, system design capabilities, and your ability to work within a team. Expect a mix of technical and behavioral questions, as well as coding challenges that may involve data structures, algorithms, and system design.

Coding and Algorithms

1. Can you implement a key-value store that supports querying for historical values?

This question tests your understanding of data structures and your ability to implement a solution that efficiently handles time-based queries.

How to Answer

Explain your approach to designing the key-value store, including how you would manage the storage of multiple values for each key along with their timestamps.

Example

“I would use a hash map to store the keys, where each key maps to a list of values and their corresponding timestamps. When querying, I would check if the key exists and then perform a binary search on the timestamps to find the appropriate value.”

2. Describe how you would optimize a function that processes a large dataset.

This question assesses your ability to analyze and improve the performance of your code.

How to Answer

Discuss the specific optimizations you would consider, such as algorithmic improvements, data structure choices, or parallel processing.

Example

“I would first analyze the time complexity of the current function and identify bottlenecks. If the function is I/O bound, I would consider using asynchronous processing. For CPU-bound tasks, I would look into optimizing the algorithm or using more efficient data structures, like hash maps for faster lookups.”

3. How would you handle error management in a microservices architecture?

This question evaluates your understanding of microservices and how to ensure reliability in distributed systems.

How to Answer

Discuss strategies for error handling, such as retries, circuit breakers, and logging.

Example

“I would implement a circuit breaker pattern to prevent cascading failures in the system. Additionally, I would ensure that all services log errors and metrics to a centralized logging system for monitoring and alerting.”

4. Can you explain the difference between synchronous and asynchronous programming?

This question tests your understanding of programming paradigms and their implications on performance.

How to Answer

Define both concepts and provide examples of when to use each.

Example

“Synchronous programming executes tasks sequentially, blocking the execution until the current task is completed. In contrast, asynchronous programming allows tasks to run concurrently, enabling other operations to proceed without waiting. I would use asynchronous programming in scenarios where I need to handle I/O operations, such as API calls, to improve responsiveness.”

5. Write a function to reverse a linked list.

This is a common coding challenge that tests your understanding of data structures.

How to Answer

Walk through your thought process and the steps you would take to implement the solution.

Example

“I would use an iterative approach, maintaining three pointers: previous, current, and next. I would traverse the list, reversing the links as I go until I reach the end.”

System Design

1. Design a system to manage user sessions in a web application.

This question assesses your ability to design scalable systems.

How to Answer

Outline the components of your system, including data storage, session management, and security considerations.

Example

“I would use a distributed cache like Redis to store session data, allowing for fast access. Each session would have a unique identifier, and I would implement expiration policies to clean up stale sessions. For security, I would ensure that session tokens are signed and encrypted.”

2. How would you design a RESTful API for a shopping cart?

This question tests your understanding of API design principles.

How to Answer

Discuss the endpoints you would create, the data models, and how you would handle authentication and error responses.

Example

“I would create endpoints for adding items to the cart, removing items, and retrieving the cart contents. Each endpoint would follow RESTful conventions, using appropriate HTTP methods. I would also implement token-based authentication to secure the API.”

3. Explain how you would ensure data consistency in a distributed database.

This question evaluates your knowledge of database management in distributed systems.

How to Answer

Discuss strategies like eventual consistency, distributed transactions, and consensus algorithms.

Example

“I would implement eventual consistency for most operations, allowing for temporary discrepancies. For critical transactions, I would use distributed transactions with a two-phase commit protocol to ensure all nodes agree on the final state.”

4. What considerations would you take into account when designing a microservices architecture?

This question assesses your understanding of microservices principles.

How to Answer

Discuss aspects like service boundaries, communication methods, and data management.

Example

“I would define clear service boundaries based on business capabilities, ensuring each service is independently deployable. For communication, I would prefer lightweight protocols like HTTP/REST or gRPC. Data management would involve each service owning its database to avoid tight coupling.”

5. How would you approach scaling a web application?

This question tests your knowledge of performance optimization and scaling strategies.

How to Answer

Discuss horizontal and vertical scaling, load balancing, and caching strategies.

Example

“I would start with horizontal scaling by adding more instances behind a load balancer. I would also implement caching at various levels, such as using a CDN for static assets and in-memory caching for frequently accessed data.”