Customers have a variety of ways to control their content cacheability on a CDN platform depending on the selected provider. Some customers prefer to use their own cache control values, while others prefer the CDN platform to apply the cache control header values for them. Most CDNs are usually very flexible and customizable with respect to the application of cache control rules.
Origin Cache Control Headers
When the CDN is configured to respect origin web server’s cache control headers. Max-age header values can be respected and used as a means of controlling content caching on the CDN platform.
Some customers prefer the use of Entity Tags (e-tag) as a means of controlling content cache. Most CDNs enable customers to elect strong, weak, or no e-tag support. When this feature is enabled, any Max-Age cache control header values that are present on the object header are discarded in favour of the e-tag value.
CDN-based Cache Control Headers
The predominant way that most customers control cacheable content on the CDN platform is via the CDN-based applications of cache control headers. Customers can apply Time-to-Live (TTL) values based on hostname, directory, extension type, as well as file names. With this level of granularity, Customers can ensure that their cacheable content will be effectively managed by the selected CDN platform. Caching values can be applied as follows: no-store (aka don’t cache the content), seconds, minutes, hours, or days.