Frontend & browser·Rendering and the browser pipeline
the page is served from the last build, and the first visitor after the timer expires triggers a fresh one in the background.
Incremental static regeneration
Also calledISR, stale-while-revalidate rendering
Static generation with a revalidation window: pages are served from cache, and after a set age the next request serves the stale copy while a rebuild happens behind it. It buys most of static's speed for content that changes on a schedule, without rebuilding the whole site. The catch is that someone always sees the stale version, and reasoning about which version a given visitor got becomes genuinely hard during an incident.