Individual skill

sql-query-optimizer

Diagnoses slow SQL from the execution plan, names the cost driver, and delivers the rewritten query plus index DDL with the expected plan change and write-side cost stated. The general entry point for slow-query work that routes deep cases to specialist skills. Use when someone asks "why is this query slow", "can you optimize this SQL", "what index do I need", "this endpoint got slow and it's the database", or pastes an EXPLAIN output. Do NOT use for deep index strategy across a whole schema - use index-advisor instead; for pure query-shape rewrites when indexes are already right - use query-rewriter instead; for ORM-driven repeated-query patterns - use n-plus-one-hunter instead; for line-by-line EXPLAIN interpretation training - use explain-plan-reader instead; for table partitioning decisions - use partition-planner instead.

skills/sql-query-optimizer/SKILL.md

Source commit 97a13607d669157a4a16d5ba79b77f208319f7b9

What was checked

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Yes

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Yes

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Yes

Observed behavior

Instructions only

Last checked

Nov 6, 2026

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