To improve frontend performance in a React/Next.js app, I’d start with code splitting and lazy-loading non-critical components using next/dynamic. For assets, I’d optimize images with the built-in component, preload critical fonts with next/font, and reduce unused CSS. For data fetching, I’d leverage SSG or ISR where possible, caching API responses with TanStack Query or SWR to avoid redundant calls. I’d also apply React optimizations like memoization, virtualization for large lists, and throttling input events. Finally, I’d monitor Core Web Vitals and use bundle analyzers to continuously improve load speed and interactivity.