Coinbase Interview Questions — Page 13

Coinbase·Software Engineer·Technical Phone Screen

Jun 2026

Coinbase SWE interview that centered entirely on a banking ledger design problem, with follow-ups that kept going deeper than I expected. The core question was straightforward enough but the extensions into atomic batches and overflow handling caught me a bit flat-footed.

Design and implement a banking ledger for n accounts with deposit, withdraw, and transfer operations. Each should return a boolean indicating success or failure, with false for invalid IDs or insufficient funds.
Write unit tests covering edge cases for this ledger: invalid account IDs, zero or negative amounts, and integer overflow scenarios.
Extend the ledger to support atomic batches of operations, where the entire batch rolls back if any single operation fails.
Analyze the time and space complexity of your implementation and walk through common pitfalls like integer overflow.

“The core implementation wasn't bad.”

View Post

Coinbase·Software Engineer·Technical Phone Screen

Jun 2026

Coinbase software engineer interview with a coding round focused on building a small banking system from scratch. Pretty straightforward premise but the edge cases pile up fast if you're not careful about your return value contracts.

Design and implement a basic banking system with three operations: registering a new user, depositing funds, and transferring funds between users. Use a single hashmap to store balances and be precise about what each operation returns on success and on every failure case.

“The core structure clicked pretty fast, one map from user id to balance, done.”

View Post

Coinbase·Software Engineer·Technical Phone Screen

Jun 2026

Coinbase software engineer interview with a coding problem centered on financial transaction logic. Pretty straightforward on the surface but the edge cases and overflow handling are where they're actually testing you.

Implement a bank account processor that takes an initial balance and a list of string operations (DEPOSIT, WITHDRAW, CASHBACK), applies each in order, and returns the final balance. WITHDRAW is ignored if funds are insufficient, and CASHBACK credits floor(balance * p / 100). Must run in O(n) time with O(1) extra space, use 64-bit integers, and include unit tests for edge cases.

“The core loop isn't hard but I fumbled on CASHBACK for a second because I tried to do floating point math before remembering they said use integers.”

View Post

Coinbase·Software Engineer·Onsite - System Design / Architecture

Jun 2026

System design round at Coinbase for a software engineering role. The whole thing was basically one big question about building a banking system from scratch, and it went pretty deep into territory I wasn't fully prepped for.

Design and implement a basic online banking system that supports account creation, deposits, withdrawals, and transfers between users. Cover the data model, API design, atomicity and idempotency of money movements, double-spend prevention under concurrent load, an immutable audit trail, security concerns, and consistency guarantees.

“This question is basically a whole interview compressed into one prompt.”

View Post

Coinbase·Data Scientist·Onsite - Cross-functional / Panel

Jun 2026

Coinbase data scientist panel round where you prep a slide deck on your proudest project and present it to a group. The follow-up questions can go pretty deep so you really can't just memorize a script and hope for the best.

Walk us through your proudest project: the problem, your approach, the key technical decisions and trade-offs you made, the impact you delivered, and what you learned from it.

“This sounds like a lot of ground to cover in one question and it is.”

View Post

Coinbase·Software Engineer·Onsite - Behavioral / Leadership

Jun 2026

Behavioral round for a software engineer role at Coinbase. Two questions, both pretty standard but they pushed for specifics so you couldn't just wave your hands at a vague project.

Walk me through the most complex project you've worked on and what your specific contributions were.
Describe a situation where you solved the same problem using more than one approach and explain your reasoning for each.

“I had a project ready but stumbled when they kept drilling into what I personally did versus what the team did.”

View Post

Coinbase·Product Manager·Onsite - Product Sense / Strategy

Jun 2026

Interviewed for a PM role at Coinbase. Just one question worth talking about but it's a classic that I fumbled more than I expected.

How do you decide whether to prioritize fixing a bug over shipping a new feature?

“I went straight to severity and user impact, which felt right, but I didn't anchor it to anything business-specific until they pushed back.”

View Post

Coinbase·Software Engineer·Onsite - System Design / Architecture

Jun 2026

Coinbase system design round for a software engineer role. The problem was a transaction query module with filtering and cursor-based pagination, which sounds manageable until you realize how many edge cases they actually want you to think through.

Design and implement a transaction query module over a dataset where each transaction has a start date, end date, user ID, and amount. The module should support per-field filters via setter methods that combine conjunctively, plus cursor-based pagination with a defined sort key, opaque cursor encoding, and handling of empty pages, end-of-results, and data mutations between page requests. Include API signatures and complexity analysis.

“This one is deceptively wide.”

View Post

Coinbase·Data Scientist·Technical Phone Screen

Jun 2026

Coinbase data scientist interview with a SQL question that looks straightforward but has a real scalability gotcha buried in it. The kind of problem where you can get a working answer pretty easily but the follow-up about performance is where they actually care.

Given a table with id and val columns, return for each row the sum of all val entries where the value is less than or equal to that row's val. Ties count fully. How do you do this without a correlated subquery that blows up on large tables?

“My first instinct was a self-join with a WHERE clause and I actually started writing it out before realizing that's exactly the O(n²) thing they were steering away from.”

View Post

Coinbase·Machine Learning Engineer·Online Assessment (OA)

Jun 2026

A multiple-select online assessment for a Machine Learning Engineer role at Coinbase covering core ML concepts. Nothing too wild, but the 'select all that apply' format is sneakier than it looks when you're second-guessing yourself on every option.

What is the difference between precision and recall, when would you prioritize one over the other, and how does F1 score relate to both?
What are the benefits and trade-offs of ensemble learning methods like bagging, boosting, and stacking, particularly around bias and variance?

“The definitions themselves are fine, I know them.”

View Post