What problem does it solve? Teams often optimize blindly, adding complexity without improving what users actually experience. This Skill enforces a measure-first workflow that identifies real bottlenecks in frontend rendering, backend queries, and database access before any code changes. ## Core Features & Use Cases - Measure-First Workflow: A five-step loop (Measure, Identify, Fix, Verify, Guard) using Lighthouse, Chrome DevTools, web-vitals RUM data, and APM tooling to establish baselines and validate fixes. - Anti-Pattern Fixes: Concrete before/after code for N+1 queries, unbounded data fetching, unoptimized images, unnecessary React re-renders, oversized bundles, and missing caching. - Core Web Vitals Targets: Threshold tables for LCP, INP, and CLS plus enforceable performance budgets checked in CI with bundlesize and Lighthouse CI. - Use Case: A product page has a 4.5s LCP. Use this Skill to profile the network waterfall, discover an unoptimized hero image and render-blocking scripts, apply responsive image markup with fetchpriority, and re-measure to confirm the improvement beats run-to-run variance. ## Quick Start Ask the agent to profile the slow page or endpoint, identify the actual bottleneck, and apply a verified fix with before-and-after measurements.