Brex Software Engineer Interview Questions + Guide in 2024

Brex is an AI-powered spend platform that empowers businesses with integrated corporate cards, banking, and global payments. Serving a wide array of clients from startups to enterprises like DoorDash, Flexport, and Compass, Brex helps companies confidently manage spend, control costs, and improve efficiency on a global scale.

At Brex, software engineers are pivotal in building innovative products and infrastructure that drive growth. The interview process typically includes several rounds focusing on coding, debugging, behavioral questions, and system design. Candidates are evaluated on technical skills and their ability to collaborate across teams and align with Brex’s values.

If you’re looking to push your limits and contribute to a dynamic engineering culture, this comprehensive guide on Interview Query will help you prepare for the position and the commonly asked Brex software engineer interview questions.

The interview process usually depends on the role and seniority; however, you can expect the following on a Brex software engineer interview:

Recruiter/Hiring Manager Call Screening

If your CV is among the shortlisted few, a recruiter from the Brex Talent Acquisition Team will contact you to verify key details like your experiences and skill level. Behavioral questions may also be part of the screening process.

The Brex Software Engineer hiring manager sometimes stays present during the screening round to answer your queries about the role and the company itself. They may also engage in surface-level technical and behavioral discussions.

The whole recruiter call should take about 30 minutes.

Technical Phone Screen

Successfully navigating the recruiter round will invite you to the technical screening round. This is usually a 1-hour interview conducted by an engineer. Questions in this stage may revolve around data structures, algorithms, debugging, and API endpoints. Brex interviewers are known to provide clear guidelines on what to expect.

Online Coding Assessment

Depending on the role, you may be given an online coding assessment through platforms like Interview Query. This involves solving several coding problems within a specified timeframe, focusing on practical, real-world scenarios rather than theoretical algorithms.

Virtual Onsite Interview

Followed by a second recruiter call outlining the next stage, you’ll be invited to attend the virtual onsite interview loop. This generally consists of multiple rounds, including:

1. Technical Coding Round: Solve coding problems, often focusing on building services, handling API responses, or debugging code.
2. System Design Round: Design a scalable and efficient system, often regarding financial transactions or credit card authorization.
3. Behavioral Round: Discuss past experiences, work culture fit, and alignment with Brex’s values.
4. Debugging Round: Locate and fix issues in a codebase. This round assesses your problem-solving approach and attention to detail.

Final Round and Offer

The final round often includes extended coding sessions with multiple mini-challenges or a live coding challenge mirroring typical Brex engineering tasks. This might include developing specific features related to Brex products and conducting a code review session with current team members.

After successfully navigating these stages, feedback will be provided promptly, followed by the offer stage if you are selected.

Typically, interviews at Brex vary by role and team, but commonly, Software Engineer interviews follow a fairly standardized process across these question topics.

1. How would you design a function to detect anomalies in univariate and bivariate datasets?

How would you design a function to detect anomalies if given a univariate dataset? What if the data is bivariate?

2. What are the drawbacks of the given student test score data layouts, and how would you reformat them for better analysis?

Assume you have data on student test scores in two layouts (dataset 1 and dataset 2). Identify the drawbacks of these layouts, suggest formatting changes for better analysis, and describe common problems in “messy” datasets.

3. What is the expected churn rate in March for customers who bought a subscription since January 1st?

You noticed that 10% of customers who bought subscriptions in January 2020 canceled before February 1st. Assuming uniform new customer acquisition and a 20% month-over-month decrease in churn, calculate the expected churn rate in March for all customers who bought the product since January 1st.

4. How would you explain a p-value to a non-technical person?

Describe a p-value in simple terms for someone who is not technical.

5. What are Z and t-tests, and when should you use each?

Explain what Z and t-tests are, their uses and differences, and when to use one over the other.

6. Write a function search_list to check if a target value is in a linked list.

Write a function, search_list, that returns a boolean indicating if the target value is in the linked_list or not. You receive the head of the linked list, which is a dictionary with keys value and next. If the linked list is empty, you’ll receive None.

7. Write a query to find users who placed less than 3 orders or ordered less than $500 worth of product.

Write a query to identify the names of users who placed less than 3 orders or ordered less than $500 worth of product. Use the transactions, users, and products tables.

8. Create a function digit_accumulator to sum every digit in a string representing a floating-point number.

You are given a string that represents some floating-point number. Write a function, digit_accumulator, that returns the sum of every digit in the string.

9. Develop a function to parse the most frequent words used in poems.

You’re hired by a literary newspaper to parse the most frequent words used in poems. Poems are given as a list of strings called sentences. Return a dictionary of the frequency that words are used in the poem, processed as lowercase.

10. Write a function rectangle_overlap to determine if two rectangles overlap.

You are given two rectangles, a and b, each defined by four ordered pairs denoting their corners on the x, y plane. Write a function rectangle_overlap to determine whether or not they overlap. Return True if so, and False otherwise.

11. How does random forest generate the forest and why use it over logistic regression?

Explain how a random forest creates multiple decision trees and combines their results. Discuss the advantages of using random forest over logistic regression, such as handling non-linear data and reducing overfitting.

12. When would you use a bagging algorithm versus a boosting algorithm?

Compare two machine learning algorithms. Describe scenarios where bagging (e.g., Random Forest) is preferred for reducing variance and boosting (e.g., AdaBoost) is preferred for reducing bias. Provide examples of tradeoffs between the two.

13. How would you evaluate and compare two credit risk models for personal loans?

1. Identify the type of model developed by the co-worker for loan approval.
2. Describe how to measure the difference between two credit risk models over a timeframe, considering monthly installments.
3. List metrics to track the new model’s success, such as accuracy, precision, recall, and AUC-ROC.

14. What’s the difference between Lasso and Ridge Regression?

Compare Lasso and Ridge Regression. Highlight that Lasso performs feature selection by shrinking some coefficients to zero, while Ridge Regression shrinks coefficients but keeps all features.

15. What are the key differences between classification models and regression models?

Explain that classification models predict categorical outcomes (e.g., spam or not spam), while regression models predict continuous outcomes (e.g., house prices). Discuss their different evaluation metrics and use cases.

16. What metrics would you use to evaluate the value of marketing channels?

Given data on marketing channels and costs for a B2B analytics dashboard company, identify key metrics to determine the value of each marketing channel.

17. How would you determine the next partner card for a company using customer spending data?

With access to customer spending data, outline the process to identify the most suitable partner for a new credit card offering.

18. How would you investigate the impact of a redesigned email campaign on conversion rates?

Analyze the increase in new-user-to-customer conversion rates following a redesigned email journey, considering other potential influencing factors.

You should plan to brush up on any technical skills and try as many practice interview questions and mock interviews as possible. A few tips for acing your Brex interview include:

1. Know the Company’s Products and Values: Study Brex’s products and values, and think about how your previous experience aligns with their mission and goals.

2. Prepare for Practical Coding Problems: Unlike many other tech firms, Brex focuses on practical, real-world coding problems relevant to their business, so be ready to build small back-end services or debug existing codebases.

3. Showcase Communication Skills: Effective communication and collaboration are highly valued. Be prepared to discuss your thought process and approach during technical problem-solving.

What is the average salary for a Software Engineer at Brex?

What feedback can candidates expect from the interview process?

Candidates often mention a mixed experience regarding feedback. While some felt positive about how recruiters provided feedback and guided them through the process, others expressed concerns about delayed or non-existent feedback. It’s best to engage actively with your recruiter for updates.

What is the company culture like at Brex?

Brex is known for its collaborative and inclusive company culture. The environment is designed to challenge the status quo and encourage continuous learning. Engineers at Brex work autonomously but with a strong sense of accountability and ownership.

If you’re ready to embrace challenges and thrive in a dynamic, fast-paced environment, this role at Brex could be the perfect next step in your career.

If you’re interested in further insights and preparation tips for your interview at Brex, check out our comprehensive Brex Interview Guide. We’ve covered a variety of interview questions that you may encounter and provided detailed guides for other roles as well.

At Interview Query, we empower you to unlock your interview prowess with a comprehensive toolkit. Equip yourself with the knowledge, confidence, and strategic guidance to conquer every interview challenge at Brex and beyond. You can also explore all our company interview guides for better preparation.

Good luck with your interview!