Brex Software Engineer Interview Questions

Brex·Software Engineer·Technical Phone Screen

Jul 2026

Coding round at Brex for a software engineer role. The problem was a card game purchase system, which sounds simple but has enough edge cases in the discount logic to trip you up if you're not careful.

Implement canPurchase and purchase methods for a gem-based card game, where players get discounts based on previously purchased cards and must pay the remaining gem cost from their current inventory.

“The discount logic is where I got sloppy at first.”

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Brex·Software Engineer·Take-home Assignment

Jul 2026

Brex take-home for a software engineering role. You build a small full-stack app that handles monetary transactions, and they want the whole thing: API, frontend, persistence, validation, tests, and a README. More involved than it sounds.

Using an AI coding assistant, build a minimal full-stack web application that supports basic monetary transactions and account balances. It should expose a REST or GraphQL API for creating credit and debit transactions, persist data, include a simple frontend to submit and view transactions, validate inputs, prevent negative balances, and come with basic tests and a README.

“The scope feels contained until you actually sit down with it.”

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Brex·Software Engineer·Recruiter / HR Screen

Jun 2026

Short behavioral screen for a software engineer role at Brex, just the one question about strengths.

What are your strengths or main advantages as a candidate?

“Pretty standard opener but I still fumbled it a bit.”

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Brex·Software Engineer·Technical Phone Screen

Jun 2026

Brex frontend coding round, one meaty React question that took up the whole session. The problem itself was well-scoped but the trade-offs discussion at the end is where things got interesting.

Build a React component that lets users multi-select colors from a dropdown, shows a count of selected colors, and renders a table of properties for each selected color. Also discuss trade-offs around state shape, performance with large lists, and accessibility.

“I jumped straight into useState for the selected set and felt pretty good about that.”

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Brex·Software Engineer·Onsite - System Design / Architecture

Jun 2026

System design round at Brex for a software engineering role. The whole session was basically one giant question about building a loyalty points engine on top of USD transactions, and they went deep on every layer. Walked out feeling like I'd covered a lot of ground but not sure I nailed any single piece.

Design a scalable service that converts USD purchase transactions into loyalty points at a fixed rate of 1 dollar = 1.5 points. Walk through the full system: API design, data model, consistency guarantees, fraud prevention, real-time vs batch processing, and rollout strategy.
How would you handle idempotency and deduplication for transaction ingestion to prevent double counting?
What consistency model would you choose between eventual and strong consistency for the points balance, and why?
How would you handle precision and rounding when converting dollar amounts to loyalty points?
How would you design the data schema to support both real-time transaction ingestion and batch processing for points calculation?
How would you design backfill and correction flows if a bug caused points to be miscalculated for a batch of transactions?
What partitioning and scaling strategy would you use for this service as transaction volume grows?
How would you build observability into this system, and what metrics or alerts would you prioritize?
How would you approach rolling out this service, including testing strategies before full launch?

“This is a beast of a question.”

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Brex·Software Engineer·Take-home Assignment

Jun 2026

Brex gave me a debugging-heavy take-home where I had to dig into a broken codebase, patch the bugs, and write a few regression tests. Pretty different from the usual leetcode grind, which I appreciated, but it also means you can't really prep for it in the traditional sense.

You're given a small codebase with failing unit tests. Find the root causes, fix the bugs, write minimal regression tests, and walk through your debugging strategy and tooling.

“This is basically a full debugging exercise compressed into one prompt.”

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Brex·Software Engineer·Technical Phone Screen

Jun 2026

Brex software engineer screen with a pretty bite-sized coding problem. Nothing crazy, but the data modeling angle made it a little more interesting than your typical leetcode grind.

Given a card with a gem cost per color and a player's gem inventory, implement a function that returns true if the player can afford the card.

“Pretty clean problem once you strip it down.”

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Brex·Software Engineer·Recruiter / HR Screen

May 2026

Pretty standard behavioral screen at Brex for a software engineer role, just walked through my work history and that was basically it.

Walk me through your work experience.

“Classic opener.”

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Brex·Software Engineer·Recruiter / HR Screen

May 2026

Short recruiter screen for a software engineer role at Brex, pretty much just the standard 'why are you looking' opener.

What's prompting you to look for a new job right now?

“Pretty much the first thing they asked.”

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Brex·Software Engineer·Onsite - Behavioral / Leadership

May 2026

Behavioral round at Brex for a software engineering role. Pretty standard set of questions but a few of them pushed harder than I expected, especially the ones around production incidents and conflict.

Tell me about a time you had to work through a problem that was poorly defined or had no clear right answer.
Walk me through a serious production issue you debugged. How did you communicate with the team while it was still happening?
Describe a situation where you had a real disagreement with a teammate. How did it get resolved?
What's a meaningful mistake you made and what changed because of it?
Why are you interested in this role specifically, and where do you see yourself going longer term?

“This is the one I fumbled a bit.”

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