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Updated weekly · Last refresh Aug 30

Costar QA Engineer Interview Questions

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

22questions
~3htotal time
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1
SQL & Data ManipulationStart here. 5 questions + 3 drills · ~70 min
Validate Data Migration IntegrityHard

Tests ability to design robust QA checks for data migration correctness and integrity.

Reconciliationtransactionsdata integrityCostar
Join Types in Real Estate SQLMedium

Tests understanding of join semantics using realistic property and listing relationships.

Joinsmany-to-onedata integrityCostar
Test Failed Database TransactionsMedium

Tests understanding of transactional behavior and QA strategies for failure scenarios.

acid propertiesnull handlingtransactionsCostar
SQL Joins and Bug FindingMedium

Evaluates SQL join proficiency and your ability to use data queries for defect investigation.

sqlCostar
SQL and QA Knowledge FitMedium

Evaluates your ability to connect SQL skills with practical QA testing and validation.

sqlCostar
SQL Average Selling PriceMedium
Practice
Practice drill

Calculate weighted average selling prices by product using a date-range join, aggregation, and NULL handling.

leetcodesqlCostarCostar Group
Top Customers by Sales RevenueEasy
Practice
Practice drill

Use GROUP BY and SUM to rank the top 10 customers by total revenue from a single sales table.

RankingGroup ByAggregationsHousecall ProEquifaxXYZ
Basic SQL and String ReverseEasy
Practice
Practice drill

Reverse Costar property search strings with PostgreSQL and flag rows whose stored expected value does not match.

sql queriesstring manipulationCostar

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2
Behavioral & Leadership17 questions · ~136 min
Prioritizing QA Under Release PressureMedium

Tests prioritization under pressure in QA, especially risk-based test selection, scope trade-offs, and ownership of release outcomes.

release planningPrioritizationresource constraintsCostar
Explaining Mobile App Identifiers ClearlyEasy

Tests technical communication, ownership, and resourcefulness when unblocking mobile QA work using app identifiers during test execution.

app identifiersmobile testingtest executionCostar
Owning an Automation Framework RedesignMedium

Tests ownership and technical leadership in improving a test automation framework, including architecture decisions, adoption, and measurable quality impact.

automation frameworkarchitectureFrameworksCostar
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The finish line: interview-readyComplete all 22 questions plus 3 hands-on drills to finish this plan.