Instacart Interview Questions — Page 10

Instacart·Software Engineer·Technical Phone Screen

Jun 2026

Instacart software engineer interview with three distinct coding problems packed into a single session. The range was pretty wide, from system design-adjacent banking logic to string parsing, and the 90-minute constraint made it feel rushed.

Design and implement a banking system that supports four core operations.
Implement a password-related algorithm, such as validating or generating a strong password.
Parse and evaluate an arithmetic expression string that includes operators and parentheses.

“This one took up most of my time.”

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Instacart·Data Scientist·Technical Phone Screen

Jun 2026

Instacart data science technical screen, one question but it was a beast. Multi-part SQL problem that starts reasonable and then keeps adding requirements until you're basically writing a mini analytics pipeline from scratch.

Given an orders table with timestamps, geo, status, and revenue components, write SQL to: (A) compute weekly revenue by ISO week excluding cancelled and refunded orders, where revenue equals subtotal plus tax plus delivery fee minus discount; (B) calculate the percent change between the last two complete weeks relative to the latest timestamp in the data; and (C) if the most recent complete week shows a drop of 4% or more versus the prior week, return the top 3 geos driving that decline, each with their share of the total revenue delta and their own week-over-week percent change.

“Part A was fine, date_trunc to Monday and filter on status = completed, standard stuff.”

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Instacart·Software Engineer·Onsite - System Design / Architecture

Jun 2026

System design round at Instacart for a software engineering role. The whole thing was basically one giant inventory question that kept branching into more sub-problems than I expected. Left feeling like I covered maybe 70% of what they wanted.

Design an inventory management system for an e-commerce platform that tracks stock across multiple warehouses and sales channels. Your design should handle cart reservations, prevent overselling under concurrent updates, and expose APIs for adjusting, reserving, committing, and releasing stock.
How would you ensure idempotency and handle retries for stock adjustment operations?
How would you design the eventing system to propagate stock change notifications to downstream consumers?
How would you reconcile inventory state with external ERP or warehouse management systems?
How would you handle backorders, returns, and system outages in this inventory system?
How would you partition and scale this inventory system to handle high write throughput across many SKUs and warehouses?

“This started as one question and then just kept expanding.”

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Instacart·Software Engineer·Technical Phone Screen

Jun 2026

Instacart SWE interview focused on designing a task-management system, then extending it with a many-to-many assignment model. The design questions got progressively more involved and the data-modeling piece was the real meat of it.

Design a task-management system supporting operations like adding, updating, deleting, and retrieving tasks, plus a TOP_K query that ranks tasks by priority with alphabetical tiebreaking on task ID.
Extend the task system so a single task can be assigned to multiple people at different times. How do you model this, and what classes or data structures do you introduce?
How would you implement ASSIGN, UNASSIGN, GET_ASSIGNMENTS_FOR_TASK, and GET_ASSIGNMENTS_FOR_USER operations efficiently?

“The TOP_K part is where I spent most of my energy.”

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Instacart·Software Engineer·Technical Phone Screen

Jun 2026

Instacart software engineering interview with a meaty in-memory system design coding problem. The whole session was basically one big question that kept growing, so if you're prepping, don't expect a clean 20-minute LeetCode warmup.

Design and implement an in-memory Task Management System with CRUD operations for tasks, where each method accepts a logical timestamp and invalid references should be handled consistently (no-op or null return).
Add priority support to tasks and implement a method that returns all existing tasks sorted by priority descending, with task ID as a tiebreaker.
Implement user management and task assignment, including a scheduleDeletion method that deletes a task at timestamp + delay, with the rule that scheduled deletions at time T must execute before any other operation at time T.
Implement a time-travel query that returns how many tasks a given user had assigned at a specific past logical timestamp, respecting all historical creates, deletes, assignments, and scheduled deletions up to that point.

“The CRUD part felt like the easy warmup but the timestamp parameter on every single method tripped me up at first.”

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Instacart·Machine Learning Engineer·Technical Phone Screen

Jun 2026

ML concepts interview at Instacart for an MLE role. One meaty theory question that turned into a back-and-forth where the interviewer kept pushing until I got to the precise answer. Not as easy as it looks on the surface.

If you use MSE as your loss function, do vanilla batch gradient descent and SGD converge to the same point?

“I said 'yes' pretty quickly because MSE is convex and I figured both optimizers are just finding the same minimum.”

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Instacart·Software Engineer·Technical Phone Screen

Jun 2026

Instacart software engineering interview with a coding round focused on building an in-memory database from scratch. Pretty straightforward premise but the details kept you honest.

Design and implement an in-memory key-field-value database supporting set, get, and delete operations, all with O(1) average time complexity.

“The core structure wasn't hard to land on, a map of maps basically.”

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Instacart·Software Engineer·Technical Phone Screen

Jun 2026

Did a coding round for a Software Engineer role at Instacart. The whole thing was basically one big object-oriented design problem that kept growing in scope. More layers than I expected for what looked like a straightforward file system question.

Design an in-memory file storage service that supports adding files, copying files, querying file sizes, and searching files by prefix and suffix. Files are identified by a full path string and have an integer size. Later parts add user ownership with storage capacity limits and a capacity update operation that evicts files when needed.

“This started simple enough.”

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Instacart·Data Scientist·Technical Phone Screen

Jun 2026

Instacart data scientist interview with a pretty gnarly SQL problem involving unpivoting a wide advertiser spend table and joining it to program financials. The question had four sub-tasks and felt more like a take-home than something you'd do live on a screen.

Given a denormalized advertiser spend table with one column per program, unpivot it into a tall format (advertiser_id, advertiser_name, program_code, spend) treating NULLs as zero, then find the single top-spending advertiser excluding those with zero total spend.
Using the unpivoted rows joined to a program financials table, identify the program with the highest net profit and the program with the highest profit margin. Return one row if they're the same program, two rows otherwise, with a reason column. Break ties by higher revenue then alphabetical program code.

“The unpivot part was fine once I remembered UNION ALL is basically the safe fallback when the dialect doesn't support UNPIVOT natively.”

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Instacart·Data Scientist·Technical Phone Screen

Jun 2026

Instacart data science interview with a meaty product analytics case that took up most of the session. The question was layered enough that I kept second-guessing whether I was going too deep on the technical side or not deep enough on the business framing.

Checkout conversion dropped from 42% to 35% week-over-week after a new promo banner was released. Traffic is flat but the marketing mix shifted toward paid social, and payment failures ticked up slightly. Walk through how you'd isolate the root cause, what queries you'd run, how you'd design a test to confirm, and what you'd present to leadership including revenue impact.

“This one ate the whole interview.”

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