Site protection: сaching and CDN

Cache Time and Revalidation

HTTP header directives are used to control caching Cache-Control .

The file storage time in the CDN cache depends on the freshness of file, which is set in one of the following ways:

• if there is a directive s-maxage, the freshness period of the file is determined by its value;
• otherwise the value is used max-age .

If no direct directives are available, a freshness assessment heuristic is used:

• by the difference between Expires and Date (if Date is greater than Expires, freshness is zero);
• in absence of Expires/Date — 10% of the difference between Date and Last-Modified;
• in absence of Date/Last-Modified — 5 minutes.

The freshness heuristic always ranges from 5 minutes to 10 days.

A file is revalidated if its lifetime has expired. The default lifetime is freshness, but some directives may affect its formula:

• min-fresh — revalidate when min-fresh seconds remain before the object lifetime expires. Reduces the actual lifetime of the file.
• max-stale — gives from cache even within max-stale seconds after freshness expiration. Increases the actual lifetime of the file.

Clearing the cache

1. Log in to the personal account, navigate to "Product/Services", click the "Site protection".
2. Select site protection service, click "Clear cache" on toolbar. After clear cache site may load slowly, until cache updated.