How Brex Interviews in 2026: Process, Questions & What They Score

1. 01

   Build a small back-end service that processes incoming card transactions: reject duplicates by idempotency key, return an error if a single card exceeds a set transaction rate per minute, and log every accepted transaction to a simple ledger.

   Tests practical service coding: idempotency keys, per-card rate limits, and a simple append-only ledger.

2. 02

   You're given an existing (buggy) codebase: find and fix the bug(s), then explain your fix.

   Tests debugging in unfamiliar code: reproduce, isolate, fix, and clearly explain the root cause.

3. 03

   Implement an idempotent payment/API endpoint that guarantees transactional correctness under retries.

   Tests idempotency design: dedupe keys, atomic writes, and safe behavior under client retries.

4. 04

   Design a scalable service that converts purchase transactions into loyalty/rewards points at a fixed conversion rate (confirmed as a Brex-attributed technical-screen question).

   Tests service design: transaction-to-points conversion with scaling and exactly-once processing concerns.

5. 05

   Design and implement a basic rate limiter.

   Tests a token bucket or sliding window implementation with per-key limits and clean data structures.

6. 06

   Build a simple credit-limit checker or transaction parser from a small spec.

   Tests spec-to-code translation: parse input, enforce limits, and handle malformed edge cases.

7. 07

   For data roles: write SQL queries involving joins, subqueries, and window functions against a transactions/fraud-style dataset.

   Tests joins, subqueries, and window functions over a transactions or fraud style dataset.

Reported problems, listed so you know what to expect. Practice them in your own editor or on the platform you prefer; SupaCV's practice mode coaches how you talk through them.

1. 01

   Design a card-authorization path that must respond within a strict low-latency budget at high transaction volume.

   System design: a strict low-latency budget at high volume, timeouts, and fallback behavior on the auth path.

2. 02

   Design a ledger system using double-entry accounting with audit logging and a nightly reconciliation process.

   System design: double-entry invariants, immutable audit logging, and a nightly reconciliation job.

3. 03

   Design a real-time fraud-detection pipeline that balances catching true fraud against false positives.

   System design: streaming feature computation, rules or model scoring, and the precision-recall tradeoff.

4. 04

   Design a rate-limited payment API with idempotency guarantees for retried requests.

   System design: combining rate limiting with idempotency so retried payments stay safe and bounded.

5. 05

   Design a service that computes rewards/points from a stream of card transactions.

   System design: stream processing with exactly-once or idempotent accrual of points per transaction.

6. 06

   Design a system to reconcile internal transaction records against an external processor/bank feed.

   System design: matching internal records to an external feed, handling gaps, duplicates, and timing skew.

Reported problems, listed so you know what to expect. Practice them in your own editor or on the platform you prefer; SupaCV's practice mode coaches how you talk through them.

1. 01

   Design a personal-finance or spend-management product for a specific user segment (e.g., college students): name the user, size the opportunity, pick a goal metric, and defend trade-offs.

2. 02

   How would you improve one of Brex's core products (e.g., the corporate card, expense management, or banking product)?

3. 03

   Brex wants to reduce fraud losses / improve new-customer onboarding / grow a particular customer segment: how would you approach it?

4. 04

   Given a vague business goal, translate it into concrete metrics, hypotheses, and an analysis plan (data-science 'problem framing' case).

5. 05

   Prioritize a set of proposed features for a product roadmap and justify the ranking.

6. 06

   How would you decide whether to build or sunset a given product line, and what data would you want first?

1. 01

   Explain the worst production bug you've shipped, how you caught it, and what you changed to prevent recurrence (posed as a 'craft'/domain deep-dive question on a past project).

1. 01

   Tell me about a time you took ownership of an ambiguous problem end-to-end: what was the outcome, and how did you measure it?

2. 02

   Tell me about a time you dealt with rejection in your personal or professional life.

3. 03

   Why are you looking to make a change right now, and what are you looking for in a role? (Be ready for a natural follow-up on why you'd join a company that was just acquired.)

4. 04

   Describe a time you had to move fast with imperfect information: how did you decide, and what happened?

5. 05

   Tell me about a time you disagreed with a decision or a teammate: how did you handle it and what was the resolution?

6. 06

   Give an example of when you had to operate outside your defined role/level to get something done ('leaders operate at all levels').

7. 07

   How do you approach giving direct feedback or holding a peer accountable?

8. 08

   Describe a time your customer-facing work directly shaped a product or process decision (customer obsession).