Database Query Performance

Diagnose database latency with explain plans, index ownership, and query-shape review. Use when a query is slow, an index is missing, or scans and N+1 patterns appear.

HoangNguyen0403 Updated 542 repo stars

File contents

Database Query Performance

Priority: P0 (CRITICAL)

Slow query work starts with the query shape and evidence, not with random index creation.

Rules

  • Capture the exact query, parameters, and access path.
  • Run explain or equivalent plan inspection before adding indexes.
  • Match indexes to filter, join, sort, and coverage needs.
  • Fix N+1 at the query pattern or loading strategy, not by caching first.

Verify

  • Explain plan was reviewed.
  • Proposed index maps to a named query path.
  • Write cost of the index is acceptable.
  • Pagination or batch loading avoids deep scans or N+1 loops.

Anti-Patterns

  • No blind indexes: every index needs a query owner.
  • No cache-first latency fix: fix query shape before hiding it.
  • No ORM opacity: inspect generated SQL when the ORM is involved.

References

HoangNguyen0403/agent-skills-standard/tree/main/skills/database/database-query-performance commit 5300afe135

Frequently asked questions

npx skillmds@latest add hoangnguyen0403/database-query-performance