Cloudflare's stale-while-revalidate support is now fully asynchronous. Previously, the first request for a stale (expired) asset in cache had to wait for an origin response, after which that visitor received a REVALIDATED or EXPIRED status.
Cloudflare, Inc., is an American technology company headquartered in San Francisco, California, that provides a range of internet services, including content delivery network (CDN) services, cloud cybersecurity, DDoS mitigation, and ICANN-accredited domain registration.