TTFB (Time to First Byte)

TTFB captures server think-time plus network latency: DNS lookup, connection setup, and how long your backend takes to generate the response. It isn't a Core Web Vital itself, but a high TTFB pushes back LCP and every other paint, so it's often the hidden cause of "my page is slow but I can't see why." Cutting it usually means caching, a CDN to shorten physical distance, faster database queries, or moving from render-on-request to static or edge-rendered pages.