Image and JavaScript optimization matter, but if the backend takes seconds to produce HTML, the experience is already degraded. TTFB measurement, eliminating N+1 queries, reducing unnecessary database work, caching stable data and response compression belong in the same performance plan.
Redcoweb journal
Core Web Vitals Are Not Only a Frontend Problem
TTFB, SSR, slow queries and server-side caching directly affect user experience and performance.