Vary Header Accept-Encoding

   The Accept-Encoding request HTTP header advertises which content encoding, usually a compression algorithm, the client is able to understand. Using content negotiation, the server selects one of the proposals, uses it and informs the client of its choice with the Content-Encoding response header.

Vary Header check for cookies

   The Vary HTTP response header determines how to match future request headers to decide whether a cached response can be used rather than requesting a fresh one from the origin server. It is used by the server to indicate which headers it used when selecting a representation of a resource in a content negotiation algorithm.

Must Revalidate HTTP Cache-Control

   Indicates that once a resource has become stale (e.g. max-age has expired), a cache must not use the response to satisfy subsequent requests for this resource without successful validation on the origin server.

Cache-Control Header Max-Age

   Specifies the maximum amount of time a resource will be considered fresh. Contrary to Expires, this directive is relative to the time of the request. this website is having max-age=600 secs.

Cloudflare

   Cloudflare, Inc. is an American web infrastructure and website security company, providing content delivery network services, DDoS mitigation, Internet security, and distributed domain name server services