Frontend & browser·State, data and re-rendering
the cached data renders instantly and a background request quietly replaces it a moment later.
Revalidation
Also calledstale-while-revalidate on the client, refetch on focus
Serving cached data immediately while fetching a fresh copy behind it, then swapping in the result. It is what makes a data-fetching library feel instant on a second visit, and it is triggered by window focus, reconnect or an interval as well as by navigation. The cost is that users can act on data that is a few seconds old, so anything with a correctness requirement needs an explicit freshness check before the mutation.