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 processesSurrogate-Control in a similar way toCache-Control in order todetermine the initial TTL (freshness) of a resource, but will preferSurrogate-Control overCache-Control if both exist.
Example
Cache-Control:max-age=0Surrogate-Control:max-age=86400, stale-while-revalidate=60