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Discuss a project where you significantly impacted performance or cost optimization.

SQLhard0.4 min read

**Situation**: BigQuery costs spiked 40% MoM from ad-hoc queries. **Task**: Reduce cost without blocking users. **Action**: (1) Identified heavy users and expensive queries. (2) Implemented partitioned tables and clustering. (3) Created materialized views for common patterns....

🤖 Analyze Your Answer
Frequency
Low
Asked at 1 company
Category
487
questions in SQL
Difficulty Split
130E|271M|86H
in this category
Total Bank
1,863
across 7 categories
Asked at these companies
EPAM
Key Concepts Tested
bigqueryoptimizationpartition

Why This Question Matters

This hard-level SQL question appears frequently in data engineering interviews at companies like EPAM. While less common, it tests deeper understanding that distinguishes strong candidates. Mastering the underlying concepts (bigquery, optimization, partition) will help you answer variations of this question confidently.

How to Approach This

This is a senior-level question that tests architectural thinking. Lead with the high-level design, then drill into specifics. Discuss trade-offs explicitly - there is rarely one correct answer. Show awareness of scale, fault tolerance, and operational complexity.

Expert Answer
76 words

Situation: BigQuery costs spiked 40% MoM from ad-hoc queries. Task: Reduce cost without blocking users. Action: (1) Identified heavy users and expensive queries. (2) Implemented partitioned tables and clustering. (3) Created materialized views for common patterns. (4) Added query cost alerts. (5) Trained users on partition pruning. Also: optimized 2-hour nightly job to 15 min via incremental. Result: 35% cost reduction; faster queries. Leadership: Drove optimization; implemented governance. Data-Driven: Used query logs for prioritization; measured before/after.

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According to DataEngPrep.tech, this is one of the most frequently asked SQL interview questions, reported at 1 company. DataEngPrep.tech maintains a curated database of 1,863+ real data engineering interview questions across 7 categories, verified by industry professionals.

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