A cached response costs zero server work and zero network: Cache-Control: max-age=31536000, immutable on a fingerprinted asset like app.a1b2c3.js means the second visit loads it from disk. The web's fastest request is the one never sent.
The two failure modes mirror each other: caching mutable content (serving yesterday's prices) and not caching immutable content (re-downloading the same bundle on every visit). The fix is naming — fingerprinted filenames can be cached forever because a change produces a new name — plus short, revalidated lifetimes on HTML.
Related terms
CDN
Content delivery network — copies of your assets on servers near your visitors, so 'far away' stops meaning 'slow'.
LCP (Largest Contentful Paint)
The moment the biggest piece of content in the viewport finishes rendering — in practice, when the page looks loaded.
Static generation (SSG)
Rendering pages to HTML at build time, so a request is answered by handing over a file instead of running code.
The bench this belongs to
Web performanceA rebuild that loads on a phone on mobile data, in the country your customers are actually in. Core Web Vitals are the measurement, revenue is the point.
