Coinbase Interview Questions — Page 3

Coinbase·Software Engineer·Technical Phone Screen

Apr 2026

Coinbase software engineer interview with a simulation-style coding problem. The drone delivery question looked deceptively simple at first but the follow-ups they mentioned made me realize I barely scratched the surface of what they were actually testing for.

You're building a 1D drone delivery simulation. A package starts at position 0 and needs to reach a target. Charging stations are given as a sorted array. The drone can fly at most 10 units per hop, and a human has to walk the package from its current position to the nearest station that's at or ahead of it before each hop. Return the total walking distance across all hops.

“I spent way too long trying to be clever about this.”

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Coinbase·Software Engineer·Onsite - System Design / Architecture

Apr 2026

System design round at Coinbase for what felt like a senior/staff backend role. The whole session was one giant food delivery design question with a bunch of follow-ups, including a knapsack optimization problem at the end that I was not expecting at all.

Design a food delivery system end-to-end, covering core entities like users, restaurants, menus, orders, and drivers, along with order lifecycle, restaurant discovery, real-time driver dispatch and tracking, payments, notifications, and how the system scales.
How would you handle peak-hour load and surge pricing or capacity in this food delivery system?
How do you ensure delivery ETA accuracy for customers?
How would you handle order cancellations and partial failures in the system, for example if payment succeeds but driver assignment fails?
Given a driver with limited carrying capacity and a delivery time window, how would you select which pending orders to bundle together to maximize efficiency? Walk through the optimization formulation and what approximation you'd use in production.

“This took up most of the session.”

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Coinbase·Software Engineer·Technical Phone Screen

Apr 2026

Coinbase SWE interview that was pretty much a knapsack problem dressed up in blockchain clothes. The follow-up on dependency trees was the part that actually made me sweat.

Given a list of transactions each with an id, size, and fee, and a block size limit of 100, how would you select a subset of transactions that maximizes total fee without exceeding the size limit?
Follow-up: if transactions have parent-child dependencies where a child transaction can only be included in the block if its parent is also included, how would you modify your selection approach?

“My first instinct was DP since it's basically a knapsack variant, but the interviewer steered me toward a greedy approach instead, sorting by fee-to-size ratio.”

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Coinbase·Software Engineer·Technical Phone Screen

Apr 2026

Coinbase software engineer interview with two parts to a transaction selection problem. The dependency extension in part two is where things got interesting and I wasn't fully prepared for it.

You have N transactions each with an id, size, and fee. Build a block capped at total size 100 that maximizes total fee. No heap allowed. Walk through your approach.
Now transactions can have parent dependencies where including a child requires including all its ancestors. How do you modify your selection strategy to respect this while still maximizing total fee?

“The no-heap constraint threw me for a second because my first instinct was literally a max-heap.”

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Coinbase·Product Manager·Onsite - Product Sense / Strategy

Apr 2026

Coinbase PM interview with two product sense questions back to back. Pretty standard format but the second part where you have to improve your own pick is where things get real.

What are the three apps you find most effective, and why?
Pick one of those apps and walk me through how you would improve it.

“I had a list ready but second-guessed myself mid-answer and swapped one out for something I thought sounded more impressive.”

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Coinbase·Software Engineer·Onsite - System Design / Architecture

Apr 2026

Did a system design round at Coinbase for a software engineer role. The question was something I hadn't seen posted anywhere before, which threw me a bit. Interviewer turned out to be pretty chill and revealed afterward that the problem was based on something he actually built early in his time at the company.

Design a system to track cryptocurrency transactions across a ledger, similar to how a crypto transaction history would be stored and queried.

“No prep material for this one since it wasn't circulating anywhere.”

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Coinbase·Software Engineer·Technical Phone Screen

Apr 2026

Coinbase software engineering interview that was basically a deep dive into iterator design in Java, all written from scratch with no IDE help. The scope was bigger than I expected, covering generics, wrapper patterns, unit tests, and complexity analysis in one shot.

In Java, define a generic Iterator interface with hasNext() and next(), implement an ArrayIterator over a fixed array, then wrap it with a PeekingIterator that adds peek() without advancing the cursor. Write minimal unit tests covering empty input, single element, multiple elements, and calling next() past the end. Analyze time and space complexity for each component.

“This felt like four questions crammed into one.”

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Coinbase·Software Engineer·Technical Phone Screen

Apr 2026

Coinbase technical screen that was basically one meaty algorithm design problem about weighted random sampling for NFT generation. Not a grind-leetcode type of question, more of a systems-thinking-meets-probability thing that I wasn't fully prepared for.

You have a set of NFT attribute categories (like ear shape or background), each with multiple possible values that have their own probabilities. Design an algorithm to randomly sample NFTs that respects those per-attribute weights, and discuss how you'd handle deduplication if every generated NFT needs to be unique.

“I started with the cumulative sum plus binary search approach because it felt safe and I could explain the math clearly.”

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Coinbase·Software Engineer·Technical Phone Screen

Apr 2026

Coinbase software engineering interview that went deep on iterator design in Java, no IDE help allowed, which was a rude awakening for muscle memory. The problem had two parts and a bunch of edge case traps that I only half-anticipated.

Design a minimal Iterator interface for integers from scratch (no IDE scaffolding), then implement a FlattenIterator that walks through a list of lists while skipping empty sublists. It must handle edge cases like empty input and repeated hasNext() calls, run in O(1) amortized time, and use O(depth) extra space.
Implement a FilterIterator that wraps any Integer iterator and only yields elements matching a given predicate. Same robustness requirements: edge cases, no invalid state on repeated hasNext() calls, O(1) amortized time.
Walk through unit tests for both iterator implementations and explain the time and space complexity of each.

“I knew the general shape of the answer but fumbled the empty sublist skipping logic on the first pass.”

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Coinbase·Frontend Engineer·Technical Phone Screen

Apr 2026

Coinbase frontend round, one meaty coding question about building a blog app that pulls from two APIs and stitches the data together client-side. More design discussion than I expected for a frontend screen.

You're building a blog app in React. Posts come from a GET /posts endpoint and include an authorId. Users come from a separate GET /users endpoint. How do you fetch and render each post with the correct author name, and show 'you' for posts belonging to the logged-in user?
How would you cache the users list, and what's your approach to loading and error states for both API calls?

“I jumped straight into fetching both endpoints in parallel with Promise.all, which felt right, then building a lookup map from userId to display name before rendering.”

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