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Brex Backend Engineer Interview Questions

The questions to prepare for a Brex Backend Engineer interview. Questions from real interview reports rank first. Updated weekly.

31questions
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1
System DesignStart here. 12 questions · ~98 min
Brex-Style Balance Check and FraudHard

Tests backend design for balance validation plus baseline fraud detection using transaction data.

fraud detectionBrex
Service Discovery and CommunicationMedium

Evaluates distributed systems fundamentals for reliable inter-service connectivity.

service discoveryarchitectureBrex
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2
Coding5 questions · ~41 min
Real-Time Transaction Validation LogicMedium

Assesses ability to design correct, low-latency validation logic for financial transactions.

Brex
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3
SQL & Data Manipulation3 questions + 3 drills · ~54 min
SQL vs NoSQL for LedgerMedium

Assesses data modeling and storage trade-offs for ledger-like financial workloads.

database designBrex
Billing Schema DesignMedium

Evaluates relational modeling for subscription billing and query efficiency.

subscription modelBrex
Calculate 30-Day User RetentionMedium
Practice
Practice drill

Use CTEs, joins, and date filtering to calculate 30-day retention by signup cohort from login and feature usage data.

Window FunctionsDate FunctionsAggregationsCurefitReachMobiIndeed
Weekly Signup Cohort RetentionHard
Practice
Practice drill

Calculate weekly retention by signup cohort using CTEs, joins, date truncation, and distinct user counts.

Window FunctionsDate FunctionsAggregationsBrexPostmaneToro
Top Spending Categories SQLHard
Practice
Practice drill

Use multi-level CTEs, joins, aggregation, and ROW_NUMBER to rank each company's top three net Brex spending categories.

Window FunctionsDate FunctionsRankingBrex
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4
Execution3 questions · ~24 min
Rate Limiting for Public APIHard

Tests ability to protect APIs using throttling strategies and correct failure behavior.

Trade-offsRisk AssessmentScope ManagementBrex
Distributed Performance BottlenecksMedium

Assesses practical performance troubleshooting and optimization approaches in distributed systems.

Problem Solvingdistributed systemsBrex
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5
Behavioral & Leadership7 questions · ~57 min
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6
More topics1 question · ~8 min
Consistency Across Service PipelinesMedium

Approach for keeping pipeline outputs consistent when multiple microservices publish overlapping, delayed, or duplicate data.

system designdata consistencymicroservicesBrex

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