Identify and fix systemic performance bottlenecks across the application lifecycle: initial load, code splitting and lazy loading, rendering (React), data fetching and caching, large dataset rendering (virtualization, streaming), and runtime memory/CPU efficiency. Deep knowledge of build tooling and delivery optimization : Webpack/Vite/Bazel, code splitting, tree-shaking, chunk strategies, lazy loading, CDN behavior, caching headers, resource hints, and their measurable impact on load performance.