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Updated weekly · Last refresh Oct 17

Costar Group QA Engineer Interview Questions

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

23questions
~3htotal time
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1
SQL & Data ManipulationStart here. 5 questions + 2 drills · ~63 min
Group By vs Having in ReportingEasy

Explain how GROUP BY forms aggregates and HAVING filters aggregated results in a reporting scenario.

Group ByHavingAggregationsCostar Group
SQL Joins and Bug FindingMedium

Evaluates SQL join reasoning and the ability to connect data issues to QA bug diagnosis.

sqlCostar Group
Join Queries for Missing ListingsMedium
Practice

Use INNER JOIN and LEFT JOIN logic to identify properties that have no active listings.

null handlingJoinsjoin typesCostar Group
Optimize a Slow SQL QueryHard
Practice
Practice drill

Rewrite a slow PostgreSQL loan payment query to reduce scanned rows while preserving the required aggregated results.

database optimizationJoinsData WranglingAmeripriseEEltro Cyberchrome PrivateEnergyHub
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
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2
Technical Fundamentals4 questions · ~34 min
Use ADB for Android TestingEasy

Tests practical Android debugging and deployment skills using ADB commands.

DebuggingCostar Group
Automate REST API TestingMedium

Tests API testing approach, tooling selection, and coverage strategy for service quality.

api testingtoolingFrameworksCostar Group
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3
Behavioral & Leadership11 questions · ~95 min
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4
More topics3 questions · ~26 min
Parallelize Test ExecutionMedium

Tests ability to improve CI/CD efficiency through parallel execution strategies.

process improvementLaunch PlanningAgileCostar Group
Maintainable Page Object ModelMedium

Tests framework design choices that reduce UI test brittleness over time.

maintainabilityautomation strategyFrameworksCostar Group
Automate Login Flow ChecksMedium

Tests practical automation skills for authentication flows and UI navigation assertions.

functionsTestingFrameworksCostar Group
The finish line: interview-readyComplete all 23 questions plus 2 hands-on drills to finish this plan.