Last updated: Jul 10, 2020
Introduction to Prefetch
CDN Prefetching is warming the CDN cache for the purpose of speeding up content delivery for those first users who would otherwise get a slow 'cache miss' response, because the CDN first needs to fetch the file from the origin server.
Another benefit of CDN Prefetching is origin offload: the origin gets less requests and consequently it's less likely your origin server and/or network will fall over or become really slow.
Prefetching is especially beneficial if you use the CDN to deliver large files and you expect new content (for example a new software download) to be requested by many users at the same time directly after publishing and you don't have Origin Shield enabled on your CDN or your CDN does not do request collapsing.
Verizon/EdgeCast has a 'Load to Edge' feature, including an API, but most CDNs do not provide a way to have the caches prefetch content from origin.
The table below shows which CDNs provide prefetching functionality and if that is free, instant, global and possible via API.
Does the CDN provide the prefetch feature? Is prefetching free or do you pay for using the feature (e.g. pay X for every 1000 prefetch requests)? Does the CDN charge for ingress data transfer (origin to CDN)?
Does the prefetching start instantly or is there a (significant) delay?
Does the CDN provide an API for loading content to their edge servers?
When prefetching, is the content loaded to all POPs?
If your CDN does not offer prefetching, find out if they offer Origin Shield
. Most likely, Origin Shield is highly effective in offloading your origing and speeding up cache miss responses.
CDNs and Prefetch
CDNs missing in this table? That is because we don't have the relevant info
= Sort of/partially
= Extra costs
More info per CDN
Prefetched content is loaded by all POPs. VideoCDN does not have a prefetch option, but content requested by a client at one POP is typically distributed immediately to other POPs too.
Akamai does not a way to prewarm the cache with specific files, but the following two (old) community articles contain useful info: Content Pre-loading / pre-warming at Akamai. Media Content Pre-loading / pre-warming at Akamai. Furthermore, know that Akamai has pretching optimizations built-in for large file delivery and streaming media. Read the Prefetching article on the Akamai Developer site.
Prefetch is available via the UI and API and available to all customers at no extra costs. On request, BaishanCloud can enable 'background cache fill'.
There is a limit of 2000 URLs per request and 60 requests per 5 minutes for each customer account in both Purge and Prefetch. How can I Purge or Prefetch files?
More info in their How to Prefetch Files article.
Prefetch is available via the UI and API and available to all customers at no extra costs (Limitation: max 100 requests per day). On request, Kingsoft Cloud can enable 'background cache fill'.
Limelight has a product/feature called Intelligent Ingest that allows for automated upload into Limelight's Origin Storage Services.
Prefetch is available via the UI and API and available to all customers at no extra costs. Without prefetch, Tencent Cloud CDN does 'background cache fill': when receiving a range request for a file that is not fully in cache, in addition to fetching and serving the range response the CDN will also fetch and store the complete file in the cache to satisfy next range requests. More info about prefetching is availaible at Prefetch Cache.
Content may be loaded to the entire network or solely to specific regions. Loading by region provides the means through which cache optimization may be targeted to regions where demand is highest. Regions are North America, US East, US Central, US West, Europe, Asia, South America. The default limit is 50 concurrent load requests at any given time. API is available. The Prefetch usually starts ~ 5 minutes after submitting the request.
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