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Instacart interview notes, page 11 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·Data Scientist·Technical Phone Screen

Jun 2026
Coding round for a Data Scientist role at Instacart. The problem was a set cover variant dressed up as a shopping optimization question, which took me a second to recognize for what it actually was.
  • Given a list of required products and a set of shoppers each covering some subset of those products, find the minimum number of shoppers needed so their combined purchases cover every required product. Return -1 if it's not possible.

“I recognized this as set cover pretty quickly, which felt good, but then I second-guessed myself mid-explanation and started rambling about greedy being optimal when it's obviously not.”

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Instacart·Machine Learning Engineer·Technical Phone Screen

Jun 2026
Coding screen for an ML Engineer role at Instacart. Just the one problem but they pushed for the optimal solution, so be ready to go beyond the brute force.
  • Given a sorted array of integers (possibly with negatives), return a new array of the squared values in non-decreasing order. Can you do it in O(n) time?

“I knew the naive version immediately, square everything and sort, but they wanted O(n) and I fumbled around for a bit before landing on the two-pointer idea.”

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Instacart·Software Engineer·Online Assessment (OA)

Jun 2026
Took the Instacart OA for a Software Engineer role and it did not go well. The main problem was an in-memory file system design question and I fumbled it pretty badly, finishing with a 450/600 which I doubt is enough to move forward.
  • Design and implement an in-memory file system that supports operations like adding files, copying files, matching files by prefix or suffix, and managing files per user.

“My brain just stopped working on the file vs.”

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Instacart·Software Engineer·Technical Phone Screen

Jun 2026
Instacart software engineer interview with a grid placement problem that sounds deceptively simple until you're actually implementing it. The non-rectangular shape handling is where things get interesting.
  • Given an empty 2D grid and four fixed shapes (each defined as a small 2D binary mask), place all four shapes onto the grid such that no two shapes overlap and each shape is placed greedily at the lexicographically smallest (row, col) origin that fits. One of the shapes is a T-shape (non-rectangular). Return the final grid or the chosen origin for each shape.

“My first instinct was to treat each shape as a bounding box, which completely breaks for the T-shape.”

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Instacart·Software Engineer·Technical Phone Screen

Jun 2026
Instacart SWE interview that went deeper than I expected on a database design problem. They took the classic in-memory DB question and layered backup/restore on top, then pushed hard on the design tradeoffs. Left feeling like I handled the mechanics okay but fumbled the discussion part.
  • Extend an in-memory key-value database with backup and restore functionality. The backup operation saves the full database state at a given timestamp and returns the count of keys that still have at least one non-expired field. The restore operation rolls back to the most recent backup at or before a target timestamp, but recalculates every restored field's TTL relative to the current timestamp so the remaining lifetime is preserved.
  • What are the tradeoffs between doing a full deep copy per backup versus using structural sharing, and how does your choice affect the behavior of subsequent write and read operations after a restore?

“I got the backup part down pretty quick, deep copy the whole state, count valid fields, store it.”

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Instacart·Software Engineer·Technical Phone Screen

Jun 2026
Instacart SWE interview that was basically a multi-part coding problem building on an in-memory database with timestamps and TTL support. The problem kept growing with each follow-up and the design discussion at the end was the part I felt least prepared for.
  • Implement setAt, setAtWithTTL, getAt, deleteAt, scanAt, and scanByPrefixAt operations on an in-memory key-field-value store where every operation takes a timestamp and TTL entries expire after a given interval.
  • How would you handle expiring entries: lazily when they are read, versus eagerly on some background tick? What are the tradeoffs?
  • If a key-field pair was set with a TTL and later setAt is called on the same pair without a TTL, what should the resulting behavior be?

“The first few operations were fine.”

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Instacart·Software Engineer·Onsite - System Design / Architecture

Jun 2026
Instacart system design round for a software engineering role. One big open-ended incident investigation question that basically ate the whole session. Felt like a senior-level bar even if the title didn't say so.
  • You're on call for a microservices banking platform and users start reporting intermittent failures and high latency on transfers at a specific time. Walk through your full troubleshooting process: what you check first, how you form and test hypotheses, how you narrow down whether the problem is in the client, network, a service, the database, or an external dependency, what mitigations you'd apply safely in the short term, and how you'd verify the fix and run a postmortem.

“This one sprawled in every direction and I kept second-guessing my own structure.”

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Instacart·Software Engineer·Technical Phone Screen

Jun 2026
Instacart SWE interview with a system design coding problem that escalates in complexity across three levels. The problem itself was interesting but level 3 is where things get genuinely hard and I felt like I was winging parts of it.
  • Build an in-memory key-value store with basic set, get, and delete operations.
  • Extend the key-value store to support TTL (time-to-live), where entries expire automatically after a given number of time units and a get on an expired key returns nothing.
  • Further extend the store so you can query the value of a key at any arbitrary past timestamp, accounting for all historical sets, overwrites, deletes, and TTLs. Discuss data structure choices and the time/space trade-offs involved.

“Pretty standard warmup.”

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Instacart·Software Engineer·Technical Phone Screen

Jun 2026
Instacart SWE interview with a probability/simulation coding question that was more stats-heavy than I expected. Not your typical leetcode grind.
  • Implement a function that estimates, via Monte Carlo simulation, the probability that an athlete will beat their personal best on a future attempt at a given event, based on their historical attempt scores.

“I knew Monte Carlo at a surface level but hadn't thought about fitting a distribution to empirical data on the fly.”

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Instacart·Software Engineer·Technical Phone Screen

Jun 2026
Instacart backend coding screen, pretty focused on interval math and salary computation. Nothing crazy but the follow-up on complexity tripped me up a bit.
  • You have a list of workers, each with an hourly rate and a set of work intervals. Given a worker ID and a time range, compute the total salary earned within that range by summing the pay for each interval's overlap with the query window.

“I got the core logic down pretty quickly, just clamp each interval to the query bounds and accumulate.”

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