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Updated weekly · Last refresh Oct 17

Illumina Data Engineer Interview Questions

The questions to prepare for a Illumina Data Engineer interview. Questions from real interview reports rank first. Updated daily.

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SQL & Data ManipulationStart here. 5 questions + 3 drills · ~70 min

Optimizing Slow Queries at ScaleHard

Explain how to diagnose and optimize a slow PostgreSQL query on large Apidel Technologies datasets.

SubqueriesJoinsData Wrangling

Illumina

Explain SQL Join TypesEasy

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

JoinsData WranglingGroup By

Illumina

SQL Querying and Data ManipulationMedium

Assesses SQL querying skills and ability to manipulate and transform data.

leetcodesql

Illumina

Complex SQL With Joins and WindowsMedium

Tests ability to write advanced SQL for analytics-style transformations.

Window FunctionsJoinssql query

Illumina

Deduplicating Data EntriesMedium

Tests ability to detect duplicates and choose appropriate SQL/data handling strategies.

Data WranglingGroup ByHaving

Illumina

Analyze Customer Purchase Trends with Window FunctionsEasy

Practice

Practice drill

Calculate the monthly spending trends for customers using window functions and joins.

The Home Depot

Aviso

Hewlett Packard Enterprise

Top Customers by Net SalesMedium

Practice

Practice drill

Compute top 10 customers by net sales using joins and aggregations, ordering by revenue with deterministic tie-breaking.

SubqueriesJoinsData Wrangling

Gain Digital

TCS

Zest AI

Top Daily Rides by VehicleMedium

Practice

Practice drill

Rank the top 3 completed rides per vehicle per day using joins, a CTE, and ROW_NUMBER.

Window FunctionsJoinsData Wrangling

Waymo

Cruise

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