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Castlight Interview Questions

The questions to prepare for Castlight interviews, across all roles. Questions from real interview reports rank first. Updated weekly.

50questions
~7htotal time
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1
ExecutionStart here. 6 questions · ~48 min
Balancing Speed Quality and ScopeHard

Describe a time you had to choose between speed, quality, and scope, and how you aligned stakeholders around the trade-off.

Trade-offsRisk AssessmentScope ManagementCastlight
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2
Pipelines6 questions · ~48 min
Data Quality in ETL PipelinesEasy

Approach for maintaining data quality and integrity across ETL pipelines.

IdempotencyData ModelingQualityCastlight
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3
Product Sense6 questions · ~48 min
Designing for Accessibility at ScaleMedium

Approach for building accessibility into product design through user needs, research, use cases, and measurable outcomes.

User NeedsPain PointsUse CasesCastlight
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4
Metrics6 questions · ~48 min
Design Success Metrics FrameworkMedium

Define a practical framework for judging design success using leading, lagging, and funnel-based product metrics.

KPIsConversion RateEngagement MetricsCastlight
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5
Strategy6 questions · ~48 min
Upsell Strategy Within Consulting EngagementsMedium

Framework for finding credible upsell opportunities inside an active consulting engagement while staying anchored in customer value and ROI.

Business AcumenGrowth Strategyclient expansionCastlight
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6
SQL & Data Manipulation6 questions + 3 drills · ~78 min
Explain SQL Join TypesEasy

Explain INNER, LEFT, RIGHT, FULL OUTER, CROSS, and SELF JOINs with examples and when to use each.

JoinsData WranglingGroup ByCastlight
Monthly Sales Trends by CategoryMedium
Practice
Practice drill

Aggregate monthly sales by product category and use LAG to calculate month-over-month changes.

InfrastructureToolsData WranglingTotal Wine & MoreInc.Benjamin Moore
Resolve Conflicting Customer AttributesMedium
Practice
Practice drill

Use joins, CTEs, and row ranking to resolve conflicting customer profile values across ACME House systems.

JoinsData WranglingQualityRamsey SolutionsACME House
Reconcile Conflicting Invoice TotalsMedium
Practice
Practice drill

Reconcile billing and ERP invoice totals using joins, a CTE for latest snapshots, and CASE-based discrepancy classification.

JoinsData WranglingQualityLiterati
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7
More topics14 questions · ~113 min
Common Pitfalls in Experiment ResultsHard

Identify the main pitfalls that can distort A/B test interpretation and explain how to guard against them.

PeekingNovelty EffectSample Ratio MismatchCastlight
Graph Traversal for Optimal PathsMedium

Tests ability to design and analyze graph traversal algorithms for optimal path or relationship finding.

ArraysStringsAlgorithmsCastlight
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The finish line: interview-readyComplete all 50 questions plus 3 hands-on drills to finish this plan.