Surrogate-Control
Alternative to Cache-Control response header for CDNs and reverse proxies.
Fastly reads this header from responses. It is proprietary to Fastly.
Fastly processes Surrogate-Control in a similar way to Cache-Control in order to determine the initial TTL (freshness) of a resource, but will prefer Surrogate-Control over Cache-Control if both exist.
Example
Cache-Control: max-age=0Surrogate-Control: max-age=86400, stale-while-revalidate=60