You now understand frontend performance optimization.
Metrics: LCP, FID/INP, CLS. Know targets.
Loading: Code splitting, tree shaking, image optimization, lazy loading.
Runtime: Virtualization, memoization, debounce/throttle.
Caching: HTTP cache, service workers, in-memory. Define invalidation.
Prefetching: Load likely-needed resources early.
Monitoring: RUM in production, segment by device and network.
Interview approach: Identify the bottleneck first, then propose targeted optimizations. Don't optimize everything blindly.