DB Query Optimization

Overview

Use this skill to improve query performance based on execution evidence, not intuition.

Scope Boundaries

• Hot-path latency or database CPU/IO usage is query-bound.
• Query plans are unstable across parameter distributions.
• Workload changes expose previously acceptable query anti-patterns.

Core Judgments

• Dominant bottleneck: scan cost, join explosion, sort spill, lock wait, network round trips.
• Rewrite scope: query shape, index changes, schema adjustment, or materialization.
• Plan stability and parameter-sensitivity risk.
• Correctness risk from aggressive rewrite or approximation.