Stale-while-revalidate configured for APIs

Every read-only API endpoint that responds with no-cache forces the browser to wait for a full network round-trip before rendering data — even for data that changes infrequently. stale-while-revalidate flips this: the browser serves the last cached response immediately (zero perceived latency), then fetches a fresh copy in the background. ISO 25010:2011 time-behaviour measures the round-trip cost; the user-visible gain is instant page paint for the common case, with fresh data arriving shortly after.

Add Cache-Control: public, max-age=60, stale-while-revalidate=86400 to API responses where serving slightly stale data is acceptable. Exclude personalized or mutation endpoints — those must use private, no-cache.

// app/api/products/route.ts
export async function GET() {
  const products = await fetchProducts()
  return Response.json(products, {
    headers: { 'Cache-Control': 'public, max-age=60, stale-while-revalidate=86400' },
  })
}