What problem does it solve? Slow applications, regressions, and wasted optimization effort happen when teams guess at bottlenecks instead of measuring them. This Skill enforces a measure-identify-fix-verify-guard workflow so every performance change targets a proven bottleneck and is kept only if re-measurement confirms a real improvement. ## Core Features & Use Cases - Measurement-First Workflow: Establishes baselines with synthetic tools (Lighthouse, DevTools) and real-user monitoring (web-vitals, CrUX) before any change, then re-measures to keep or revert. - Anti-Pattern Fixes: Provides concrete before/after code for N+1 queries, unbounded fetching, connection pool exhaustion, missing image optimization, React re-renders, large bundles, and caching mistakes. - Database Query Analysis: Guides reading EXPLAIN ANALYZE output, designing composite indexes for the query shape, and recognizing when indexes will not help. - Use Case: A page's INP is 240ms. Profile the main thread, find long tasks from an unvirtualized list, apply virtualization, re-measure to 90ms, log the attempt, and add a CI bundle budget plus RUM alerting to guard against regression. ## Quick Start Ask the agent to profile your slow page or API endpoint and propose a measured performance fix following the optimization workflow.