To succeed in the Brex interview process, you need to be exceptionally prepared across several core competencies. Below is a detailed breakdown of the primary evaluation areas.
Product Analytics & Metrics Design
Understanding the "why" behind user behavior is crucial. This area tests your ability to define success metrics, identify root causes for metric shifts, and propose product improvements based on data. Strong performance means you do not just list standard metrics; you tailor them specifically to Brex's B2B financial products.
Be ready to go over:
- Metric formulation – Defining primary, secondary, and guardrail metrics for a new feature launch.
- Root cause analysis – Investigating a sudden drop in corporate card usage or an increase in expense reporting drop-offs.
- User lifecycle analysis – Measuring activation, engagement, and churn in a SaaS or fintech context.
- Advanced concepts (less common) – Cannibalization effects, network effects in B2B payments, and sophisticated LTV/CAC modeling.
Example questions or scenarios:
- "If the activation rate for our new integrated travel booking software dropped by 15% week-over-week, how would you investigate the cause?"
- "How would you design a dashboard to monitor the health of our global payments product?"
- "What metrics would you use to evaluate whether a new automated receipt-matching feature is successful?"
Applied Statistics & Experimentation
Because Data Scientist roles at Brex heavily influence product strategy, you must be highly proficient in designing and evaluating A/B tests. Interviewers want to see that you understand the mathematical principles behind experimentation and can identify when standard A/B testing is not appropriate.
Be ready to go over:
- Experiment design – Choosing randomization units, determining sample sizes, and defining minimum detectable effects (MDE).
- Statistical concepts – P-values, confidence intervals, statistical power, and Type I/Type II errors.
- Handling practical challenges – Dealing with novelty effects, day-of-week seasonality, and non-normal distributions.
- Advanced concepts (less common) – Causal inference, synthetic control methods, and multi-armed bandits.
Example questions or scenarios:
- "Design an experiment to test a new onboarding flow for enterprise customers. What are the potential pitfalls?"
- "How would you analyze an A/B test where the sample size is extremely small due to targeting a niche segment of startup founders?"
- "Explain how you would handle interference or network effects if we tested a new referral program."
Technical Execution (SQL & Python/R)
You cannot treat data as a product if you cannot extract and manipulate it efficiently. This area evaluates your hands-on coding ability. Strong candidates write optimized, readable code and are comfortable navigating complex, messy datasets.
Be ready to go over:
- Advanced SQL – Complex joins, window functions, CTEs (Common Table Expressions), and aggregations.
- Data manipulation in Python/R – Using Pandas or Dplyr to clean, merge, and transform data.
- Edge cases – Handling null values, duplicates, and data anomalies gracefully.
Example questions or scenarios:
- "Write a SQL query to find the top 3 spending categories for each company in the last 30 days, accounting for potential refunds."
- "Given a raw dataset of user login events and transaction timestamps, write a Python script to calculate the average time to first transaction."
Behavioral & Cross-Functional Collaboration
Brex values a diverse team and an inclusive culture where ownership runs deep. This area evaluates how you work with Product Managers, Engineers, and business leaders. Strong candidates demonstrate a history of taking initiative, resolving conflicts through data, and communicating complex technical concepts to non-technical audiences.
Be ready to go over:
- Stakeholder management – Pushing back on flawed product assumptions using data.
- Navigating ambiguity – Taking a vague business question and turning it into a concrete analytical project.
- Impact and leadership – Examples of when your insights directly changed a product roadmap or saved the company money.
Example questions or scenarios:
- "Tell me about a time you had to convince a skeptical Product Manager to change their strategy based on your data."
- "Describe a situation where you had to deliver an analysis with incomplete or messy data."