Performance optimization: built-in features (code-splitting, preloading, coalescing, inlining, prerendering), diagnosing tools (PageSpeed Insights, WebPageTest, devtools), asset optimization (images with enhanced-img, video compression, font subsetting/preloading), code reduction (latest Svelte, package analysis, server-side analytics, dynamic imports), navigation (link preloading, promise returns, waterfall prevention via server load functions and database joins), hosting (same-datacenter backend, edge deployment, CDN images, HTTP/2+).