Refresh cached content in advance, before its time-to-live (TTL) you set in the the Caching behavior expires, so that end-users don't have to wait for a response from the origin.

How it works

If a client requests an object after the asynchronous refresh begins—but before the TTL expires—the edge server continues to serve the older object to the client until the TTL expires, or the edge server receives the refreshed object from the origin.

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You can't use this behavior if you selected Honor origin Cache-Control and Expires or Honor origin Expires headers in the Caching behavior.

Implementation

Set the slider to the percentage of an object’s TTL after which you would like the ​Akamai​ edge server to asynchronously refresh the object in cache.

If, for example, an object has 10 minutes to live, and a response from the origin takes 30 seconds, the optimal setting would be 95% or lower of the object’s time to live.

This way, the object is refreshed early enough for the users to receive that object without having to wait for the response from the origin, but not too much in advance so as not to increase load on the origin.

Be aware that the percentage you choose depends on:

1. The frequency of end user requests. Setting too high percentage and having too few requests could mean the object expires and an end user must wait for the response from the origin.
2. The length of time for the origin to send the whole response. If the origin hasn't finished sending the new object by the time the original object expires, then users have to wait for the origin to respond.