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Updated weekly · Last refresh Aug 30

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 weekly.

22questions
~3htotal time
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1
SQL & Data ManipulationStart here. 4 questions + 3 drills · ~62 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
Regression Test Data CleanupMedium

Tests test isolation practices to keep automated suites reliable and repeatable.

Reconciliationtransactionsdata integrityCostar Group
Verify Web Form PersistenceMedium

Tests end-to-end validation from UI input to database persistence in a web app.

Data WranglingReconciliationdata integrityCostar Group
SQL Joins and Bug FindingMedium

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

sqlCostar 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
Calculate Monthly Sales Growth by Product CategoryMedium
Practice
Practice drill

Calculate month-over-month sales growth for each product category using JOINs and window functions.

JoinsAggregationsWayfairREVOLVEFanatics
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
2
Behavioral & Leadership16 questions · ~129 min
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 Group
Reporting a High-Impact BugEasy

Tests QA ownership, bug reporting clarity, and how effectively you drive action on a difficult defect.

Stakeholder ManagementCommunicationOwnershipCostar Group
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3
More topics2 questions · ~16 min
Parallelize Test ExecutionMedium

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

process improvementLaunch PlanningAgileCostar Group
Automate Login Flow ChecksMedium

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

functionsTestingFrameworksCostar Group

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