Process, Questions & AI Prep Tips
Brex is a corporate fintech company reinventing business banking, corporate cards, and spend management for startups and enterprises. Engineering interviews emphasize financial systems reliability, credit risk infrastructure, fraud prevention, and high-quality API design. Brex runs a largely Elixir and Go stack and values engineers who write clean, well-tested code.
A 30-minute call covering your background in fintech or financial infrastructure, your interest in corporate spend management, and basic technical experience.
A 60-minute coding session typically using Elixir, Go, or your preferred language. Problems cover algorithms, data structures, and may include a financial domain scenario.
Design a Brex system such as the corporate card transaction processing pipeline, real-time fraud detection, or a multi-entity spend limit enforcement system.
Two to three rounds covering advanced coding, a deeper systems discussion around financial compliance or API design, and a behavioral interview assessing ownership and engineering craft.
Design Brex's corporate card transaction authorization system that runs in under 100ms.
How would you build a real-time spend limit enforcement system across multiple cards and employees?
Design a fraud detection pipeline that scores every card transaction within 50ms.
How would you architect the Brex rewards and cashback calculation engine?
Design the corporate card bill payment and reconciliation system.
How would you build an expense policy engine that automatically flags out-of-policy spend?
Design the Brex API used by finance teams to integrate spend data with accounting software.
Implement an idempotent payment processing service with retry and deduplication logic.
How would you design a credit underwriting service that evaluates startup creditworthiness in real time?
Tell me about a time you improved the reliability of a financial system under high load.
Familiarize yourself with Elixir and the actor model — Brex is one of the largest Elixir users in production and this shapes their architecture discussions.
Study idempotency and distributed transactions carefully — these are foundational concepts for every financial system Brex builds.
Understand the mechanics of charge card vs credit card billing cycles and how spend limits work across an organization hierarchy.
Brex values clean, idiomatic code — in coding rounds, prioritize readability and correctness over clever optimizations.
Prepare examples of working closely with product and finance teams to build reliable financial infrastructure.
Review PCI-DSS compliance basics and how card networks authorize and settle transactions.
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