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Instacart interview notes, page 2 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

Apr 2026
Bizops interview at Instacart with a SQL-heavy analytical question focused on driver efficiency. Pretty straightforward setup but the metric definition was the tricky part.
  • Write a SQL query to find the least efficient driver based on deliveries completed per hour of driving time over the last two months.

“The SQL itself wasn't the hard part.”

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Instacart·Software Engineer·Onsite - System Design / Architecture

Apr 2026
System design round at Instacart focused entirely on building an inventory management system for a grocery delivery context. Pretty dense problem with a lot of moving parts, and the conversation went deep fast.
  • Design an inventory management system that supports updating stock levels across multiple stores and warehouses, reserving items so two customers can't claim the same unit, and a pickup/collection API that finalizes the deduction. Walk through your database schema and how you maintain strong consistency to prevent oversell.
  • How would you handle reservation TTLs and cleaning up expired reservations so stock is released back to available inventory?
  • How do you make the pickup/collection API call idempotent so a retry doesn't deduct inventory twice?
  • Hot SKUs create single-row contention in the stock table. How would you architect around that?
  • How would you scale reads versus writes differently for this inventory system?

“This is a meaty one.”

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Instacart·Software Engineer·Technical Phone Screen

Apr 2026
Interviewed for a software engineer role at Instacart and got a string decoding problem involving nested bracket patterns. Pretty classic stack-based question but the nesting part is where things get interesting.
  • Implement a function to decode an encoded string where a number followed by a bracketed substring means that substring repeated that many times. Patterns can be nested inside each other.

“The simple cases like '3[a]2[bc]' are easy enough to reason through, but the nested version like '3[a2[c]]' is where I had to slow down and actually think about the stack structure.”

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Instacart·Software Engineer·Technical Phone Screen

Apr 2026
Interviewed for a Software Engineer role at Instacart and got a pretty involved coding round built around simulating bus routes. Four tasks stacked on top of each other, each one extending the last, which I wasn't fully expecting.
  • Given a large list of passenger events for a bus simulation, implement a downsampling function that reduces the passenger count by a given factor while preserving the distribution across origin-destination pairs.
  • Implement the core bus simulation: for each scheduled bus arrival, drop off passengers whose destination matches the current stop, then board waiting passengers without exceeding bus capacity, and emit a log entry for every board and drop action.
  • Given a potentially buggy simulation log, write a validator that checks whether bus occupancy ever goes negative or exceeds capacity, and whether any passenger boards more than once or drops off without having boarded.
  • Extend the boarding logic to support priority passengers: passengers with a priority pass should board before regular passengers at each stop, with tie-breaking by appear_time and then passenger_id. Capacity constraints still apply.

“My first instinct was to just randomly sample the whole list, which is wrong because you'd skew the OD distribution.”

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Instacart·Software Engineer·Technical Phone Screen

Apr 2026
Got a coding round at Instacart for a software engineer role and the question was a full arithmetic expression evaluator. More involved than I expected for a phone screen, covering parsing, precedence, unary minus, and error handling all at once.
  • Implement an evaluator for a string arithmetic expression that handles +, -, *, /, parentheses, spaces, operator precedence, left-to-right associativity, unary minus, truncating integer division, and returns a 64-bit integer. Also handle errors like mismatched parens or division by zero. Describe your approach and its complexity.

“I went with recursive descent because I can never remember the two-stack approach under pressure, and it felt more natural to reason about.”

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Instacart·Software Engineer·Technical Phone Screen

Apr 2026
Instacart SWE interview with a scheduling/queueing problem that started simple and got progressively harder. The follow-ups on multi-clerk scaling are where things got real.
  • Given n grocery pickup orders, each with an arrival time and a service duration, compute the average waiting time for all shoppers. The clerk processes one order at a time and waits if idle. Arrival times may need to be sorted first.
  • Extend the solution to k identical clerks. Each arriving order goes to whichever clerk becomes free the earliest. Return the average waiting time and justify your choice of data structures and the time complexity.
  • How does your approach scale for very large n, say up to 200,000 orders? What are the time and space complexities?

“The single-clerk version felt manageable.”

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Instacart·Software Engineer·Technical Phone Screen

Apr 2026
Instacart software engineer interview with two distinct coding problems, each with multiple follow-ups that layered on complexity. The file parsing one felt manageable at first but the password reconstruction follow-up tripped me up, and the expression evaluator was basically a graph problem in disguise.
  • You're given a text file with a block that starts with a coordinate header like "[2,4]", followed by rows of equal-length characters. Write code to return the character(s) at each specified coordinate, where [0,0] is the bottom-left of the block.
  • Follow-up: now each block also has an integer at the top indicating that block's position in a password. Parse multiple blocks and reconstruct the password by placing each block's extracted character at its indicated index.
  • Second follow-up: keep reading blocks until you see a repeated index value. That repetition signals the start of a new password. Return only the first complete password.
  • Given a target variable and a list of assignments (e.g., T1=1, T2=2, T3=T4, T4=T5, T5=T2), resolve the numeric value of the target by following the dependency chain.
  • Follow-up: assignments can now include exactly one addition or subtraction operator (e.g., T3=T4+T5). Extend your solution to handle this arithmetic.
  • Second follow-up: if the dependency graph contains a cycle (e.g., T4 depends on T5 and T5 depends on T4), return "IMPOSSIBLE" instead of looping forever.

“The coordinate system tripped me up for a second because [0,0] being bottom-left means you have to flip the row index.”

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Instacart·Software Engineer·Onsite - System Design / Architecture

Apr 2026
System design round at Instacart for a software engineering role. The whole session was basically one big question that kept getting harder, which I wasn't fully prepared for.
  • Design and implement a versioned key-value store with set(key, value, timestamp) and get(key, timestamp) operations, where get returns the most recent value at or before the given timestamp.
  • How would you handle very large timestamp ranges and memory constraints in this key-value store?
  • Extend the API to support delete operations, time-range queries, and background compaction. How does that change your design?

“I started with a sorted list per key and binary search, which is the obvious answer.”

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Instacart·Software Engineer·Technical Phone Screen

Apr 2026
Instacart data or analytics interview with a SQL-style question about ranking employees by office time, filtered to a specific job title. Short and focused, nothing too wild.
  • Given a dataset of employee office visit logs, find the top N employees by total time spent in the office, but only for a specific job title.

“Pretty standard ranking query but the title filter is where people slip up if they apply it after the ranking instead of before.”

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Instacart·Software Engineer·Onsite - System Design / Architecture

Apr 2026
Instacart system design round for a software engineering role. The whole session was one big question about e-commerce category pages, which sounds narrow until you realize how many rabbit holes it opens up.
  • Design the backend and serving architecture for an e-commerce category page (like /electronics/phones) that supports faceted filtering, multiple sort options, pagination or infinite scroll, SEO-friendly rendering, caching for high-traffic categories, optional personalization, and near-real-time inventory and price updates. Cover your API design, data models, search and indexing strategy, ranking signals, cache hierarchy, read/write patterns, consistency tradeoffs, scaling to millions of SKUs and tens of thousands of QPS, and how you'd approach A/B testing and monitoring.

“This question is basically five system design questions stapled together.”

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