Fast Purge lets you purge content using the invalidate and delete methods.
This purge method marks the cached content as invalid. The next time the Akamai edge server receives a request for the content, it sends an HTTP conditional GET (If-Modified-Since) request to the origin. If the content has changed or the origin does not support Last-Modified headers, the origin server returns a full fresh copy; otherwise, the origin normally responds that the content has not changed, and Akamai can serve the already-cached content.
This purge method removes the content from Akamai edge server caches. The next time the edge server receives a request for the content, it retrieves the current version from the origin server. If it cannot retrieve a current version, it will follow the instructions in your edge server configuration.
Invalidate vs. delete
Invalidate is the default behavior most typically required. When using Invalidate, objects are not removed from cache and full objects are not retrieved from your origin unless they are newer than the cached versions. Delete can increase the load and bandwidth on your origin more than Invalidate because Delete results in retrieving the full object from the origin every time. When configured to do so, Invalidate is also preferable because it allows the Akamai edge server to continue to serve stale content to your end users if the origin is unreachable.