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Explain the process you would follow for optimizing a database query that is running slow.

SQLmedium0.5 min readPremium
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
Amazon
Key Concepts Tested
joinpartitionwindow
Expert AnswerPremium
90 wordsInterview-ready
**Systematic approach**: (1) **Profile**: EXPLAIN ANALYZE—identify seq scans on large tables, costly hash joins, sort spills. (2) **Baseline**: Current runtime, row counts, data distribution. (3) **Index**: Add B-tree/hash on filter and join columns; verify usage in plan. (4) **Statistics**: Run ANALYZE; planner accuracy affects join order. (5) **Rewrite**: Replace correlated subqueries with JOINs or window functions; push predicates. (6) **Partition**: Prune by partition key....
The complete answer continues with detailed implementation patterns, architectural trade-offs, and production-grade considerations. It covers performance optimization strategies, common pitfalls to avoid, and real-world examples from companies like Amazon. The answer also includes follow-up discussion points that interviewers commonly explore.

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