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Instacart interview notes, page 4 of 13

Large Enterprises

Most of these Instacart write-ups come from Software Engineers (88), then Data Scientists (28) and Machine Learning Engineers (5). The most reported rounds are the technical phone screen (93), the system design round (13), the behavioral / leadership round (6) and the product sense round (6).

128 interview notes · updated Jul 2026

Instacart·Software Engineer·Technical Phone Screen

May 2026
Instacart software engineering interview with a simulation-style coding problem that starts simple and then throws a multi-worker follow-up at you. The problem itself was interesting but the complexity analysis at the end is where things get real.
  • You're building a last-mile delivery simulator with a single shopper. Given n orders each with an arrival time and a service time, the shopper processes one order at a time and is idle until the next one arrives. Compute the average waiting time across all customers, where waiting time is finish time minus arrival time. Return a float rounded to 5 decimal places.
  • Follow-up: extend the simulator to k shoppers (k >= 1). Orders must be processed strictly in arrival order and each new order goes to whichever shopper is free earliest, breaking ties by smallest shopper ID. Compute the average waiting time and analyze the time and space complexity of your solution.

“The single-shopper version is pretty mechanical once you track when the shopper becomes free.”

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Instacart·Software Engineer·Technical Phone Screen

May 2026
Instacart software engineer interview that went deep on data transformation and pandas. The question was meaty enough that I kept second-guessing whether they wanted a code walkthrough or a design discussion, and by the end I think I gave them a weird hybrid of both.
  • Given a transactions dataset with user_id, category, subcategory, amount, and an ISO timestamp, implement two pivot table transformations in Python: first, rows as category and columns as YYYY-MM months with summed amounts (zero-filled for missing cells); second, rows as (user_id, category) pairs and columns as subcategory with row counts. Also outline an equivalent SQL approach, discuss null handling, timezone issues, chunking for large data, and a top-K column strategy with an OTHER bucket. State time and space complexity.

“This was a lot to unpack and I kind of froze for a second deciding where to start.”

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Instacart·Software Engineer·Onsite - Behavioral / Leadership

May 2026
Behavioral round at Instacart for a software engineer role, focused pretty squarely on past challenges and accomplishments. Nothing too surprising but the questions had some teeth if you weren't prepared to get specific.
  • What is the most significant professional challenge you have faced, and how did you handle it?
  • Tell me about a specific accomplishment you are most proud of. Walk me through your role, the actions you took, the measurable impact, any trade-offs you made, and what you learned.

“I had a story ready but fumbled the 'how you handled it' part because I kept circling back to context instead of just saying what I actually did.”

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Instacart·Software Engineer·Technical Phone Screen

May 2026
Instacart SWE interview threw a pretty meaty string validation problem at me that I thought I had under control until the follow-up questions started piling on.
  • Given a password policy (length 8-20 chars, must have at least one lowercase, one uppercase, one digit, no character repeated 3+ times consecutively), write a function that validates a string and, if invalid, returns the minimum number of insert/delete/replace edits to make it compliant plus one valid corrected password. Walk through your algorithm, handle large inputs, and analyze time and space complexity.

“I started with the validation part, which felt fine, just a regex pass and a length check.”

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Instacart·Software Engineer·Technical Phone Screen

May 2026
Karat screen for a Software Engineer role at Instacart. The coding portion went sideways pretty fast, ran out of time on the main problem and didn't get to run the code, which sealed the outcome.
  • Given a list of stock record objects (each with a date and a price), find the largest absolute price change between chronologically adjacent days. Return the two dates and the price difference.

“The part that tripped me up wasn't the algorithm itself, it was figuring out how to extract fields from the record objects.”

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Instacart·Software Engineer·Technical Phone Screen

May 2026
Instacart coding round, one meaty problem the whole time. The question was about evaluating arithmetic expressions from scratch, which sounds manageable until you're actually writing a recursive parser under pressure.
  • Given a string containing an arithmetic expression with non-negative integers, the four basic operators, parentheses, and optional spaces, evaluate it and return the result as a 64-bit integer. Division should truncate toward zero. Your solution should handle operator precedence, unary minus, and be implemented using depth-first traversal (either recursive descent or a stack-based simulation). Also discuss time and space complexity, recursion depth concerns, and how you'd convert to an iterative approach.

“This wrecked me a little.”

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Instacart·Machine Learning Engineer·Technical Phone Screen

May 2026
Interviewed for an MLE role at Instacart, got a pretty standard coding question but with a twist that I almost missed entirely.
  • Given a sorted array of integers, return a new array of the squared values, also in sorted order. Then optimize it to run in linear time.

“My first instinct was just square everything and sort it, which works but they pushed back immediately asking if I could do better.”

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Instacart·Software Engineer·Technical Phone Screen

May 2026
Interviewed for a software engineer role at Instacart. Two coding problems back to back, one systems-flavored and one pure algorithm. Nothing too wild but the combo felt deliberate.
  • You have a very large password file. Write a program that reads only the required password(s) from it while keeping memory usage as low as possible. How do you ensure only the necessary data is loaded into memory?
  • Given a mathematical expression as a string, implement a program to evaluate it using a depth-first search approach.

“My first instinct was to just read the whole file and filter in memory, which is exactly the wrong answer.”

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Instacart·Software Engineer·Technical Phone Screen

May 2026
Coding screen for a software engineer role at Instacart. One problem the whole time, string decoding with a stack, but the follow-ups kept coming and that's where things got interesting.
  • Given a nested encoded string where digits followed by parentheses mean 'repeat the contents k times', decode it manually using a stack. No regex allowed.

“The base case was fine.”

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Instacart·Software Engineer·Onsite - System Design / Architecture

May 2026
System design round at Instacart focused entirely on inventory management for e-commerce. The problem had a lot of moving parts and I felt like I was playing catch-up the whole time trying to cover schema, concurrency, and APIs without losing the thread.
  • Design an inventory management system for an e-commerce platform that handles stock updates, checkout reservations to prevent overselling, and a curbside pickup or warehouse picking workflow.

“This was one question but it sprawled into like five different conversations.”

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