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Updated weekly · Last refresh Aug 30

66degrees Data Engineer Interview Questions

The questions to prepare for a 66degrees Data Engineer interview. Questions from real interview reports rank first. Updated weekly.

30questions
~4htotal time
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1
SQL & Data ManipulationStart here. 6 questions + 2 drills · ~71 min
Top Customers by Sales RevenueEasy
Practice

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

RankingGroup ByAggregations66degrees
OLTP vs OLAP Database DesignMedium

Explain OLTP vs OLAP designs, including schema shape, workload patterns, and when each is appropriate in a data platform.

financial dataperformanceData Modeling66degrees
Database Performance in Relational SystemsMedium

Tests your approach to indexing, query plans, and tuning for relational databases.

Window FunctionsJoinsAggregations66degrees
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
Contact Center Agent Performance MetricsHard
Practice
Practice drill

Compute daily agent call KPIs and SLA using joins, aggregations, and window ranking in a contact center model.

ETLAggregationsData ModelingADP
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2
Pipelines20 questions · ~171 min
Cloud Platform Experience for PipelinesMedium

Describe practical experience building pipelines on AWS, including orchestration, security, and data quality.

InfrastructureETLData Modeling66degrees
Data Quality in ETL PipelinesEasy

Approach for maintaining data quality and integrity across ETL pipelines.

IdempotencyData ModelingQuality66degrees
Design Real-Time Operations Dashboard PipelineHard

Design a pipeline for a real-time operational dashboard, covering streaming ingestion, modeling, data quality, and dashboard serving.

InfrastructureStream ProcessingQuality66degrees
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3
Coding4 questions · ~34 min
Python Libraries for Data WorkEasy

Tests your practical Python tooling for data transformation and analysis workflows.

Hash TablesArraysSorting66degrees
Streaming Data Processing in PythonHard

Tests your ability to design Python code for streaming ingestion and processing patterns.

Hash TablesQueueArrays66degrees
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The finish line: interview-readyComplete all 30 questions plus 2 hands-on drills to finish this plan.