query-performance-tuning

What problem does it solve?

This Skill helps you quickly identify why a database query is slow and choose the safest, highest-leverage fix by interpreting execution plans, index behavior, and working-set limits.

Core Features & Use Cases

• Diagnostic workflow before indexing: Confirm slowness, capture an actual plan with realistic parameters, identify the dominant slow node, then classify the root cause (wrong plan, wrong access path, or wrong working set).
• EXPLAIN interpretation: Read the plan effectively (sequential vs index scans, row estimates vs actuals, filter effectiveness, sort/hash join behavior) for PostgreSQL- and MySQL-style signals.
• Indexing and N+1 remediation: Recommend the right index shape (including composite/covering/partial patterns) and detect/fix N+1 query patterns common in ORM-heavy codebases.
• Denormalization vs indexing decision: Provide a rule-based approach to when denormalization (computed columns, materialized views, or read stores) becomes warranted.
• Working-set sizing and capacity actions: Determine whether the issue is disk-bound thrashing and select interventions like memory scaling, partitioning, archiving, or index bloat recovery.

Quick Start

Use it when you see that a request is slow and you want the fastest path to an actionable diagnosis: generate a slow-query tuning report for the specific SQL and its EXPLAIN ANALYZE output (with realistic parameters) explaining the failure mode and the most likely fix.