Checkout
Milliseconds saved at the Buy button are orders, not UX polish.
Live storefront studies put conversion several percent lower for every additional 100ms of Largest Contentful Paint, with a similar slope on interaction delay. High-volume checkout already treats sub-second as the job.
LCP → conversionIndexation
Googlebot spends crawl on origins that answer quickly.
Crawl capacity rises when response times stay low and stable, and falls when TTFB stretches or 5xx appear. That is not a content-strategy problem. A slow first byte is fewer URLs fetched, slower recrawl on new pages, and Core Web Vitals you cannot design around once the origin is late.
TTFB → crawlPaid traffic
The click is paid. The landing page still has to show up.
Every delayed LCP on a paid landing page is wasted CPA. The auction already happened. Speed here is not a Lighthouse badge. It is whether the session you bought becomes a lead, a sale, or a bounce that retargeting has to buy again.
CPA → yield