I interviewed with Brex earlier this year.

The first round was a phone screen, LeetCode Hard level, but the interviewer was very helpful and gave hints, after which I was able to solve.

Onsite:

• Debugging round: The code had bugs that were a bit confusing. You are expected to debug a few unit tests and an integration test. It's a little tricky to find the buggy spots. You need to pay close attention.
• Behavioral: Describe-a-time type questions.
• Coding: You need to make REST calls. I used Java and wasted all the time just doing warm-up. I couldn't complete even that. Java is highly not recommended. The recruiters themselves recommend using a dynamically typed language. I would have done really well had I chosen some other language. But that's how one learns from mistakes. Be prepared to make REST calls and parse JSON.
• Design: Typical System Design interview as in the industry, with a special focus on the database side.

Debugging Round: You have to find bugs. Being familiar with Java 8 data classes will greatly help.

Coding Round: Make REST calls, parse JSON, and then sort.

Values: Behavioral questions.

Design Round: Industry-standard system design questions. Your approach and knowledge will be judged.