What problem does it solve? Web applications slow down through N+1 queries, oversized bundles, unoptimized images, and render-blocking resources, but teams often optimize blindly without profiling data. This Skill enforces a measure-first workflow that identifies real bottlenecks, fixes them, verifies the improvement, and guards against regressions. ## Core Features & Use Cases - Measurement-First Workflow: Follows a five-step loop (measure, identify, fix, verify, guard) using Lighthouse, Chrome DevTools, web-vitals RUM data, and backend query logging. - Anti-Pattern Fixes: Provides concrete code fixes for N+1 queries, unbounded data fetching, missing image optimization, unnecessary React re-renders, large bundles, and missing caching. - Core Web Vitals Targets: Defines thresholds for LCP, INP, and CLS plus enforceable performance budgets for bundle size, API latency, and Lighthouse scores in CI. - Use Case: When users report a sluggish dashboard, profile the interaction in DevTools, find long tasks blocking the main thread, apply code splitting or memoization, then re-measure against the baseline and revert if the gain is within noise. ## Quick Start Ask the AI to profile the slow page load on the dashboard route and fix the identified bottleneck following the performance-optimization workflow.