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CDN Guide » Prefetch

Last updated: Apr 13, 2017

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 potentially large 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 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.

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.
Read on to learn more about the differences between CDNs.

Instant
Does the prefetching start instantly or is there a (significant) delay?

Free
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)?

API
Does the CDN provide an API for loading content to their edge servers?

All POPs
When prefetching, is the content loaded to all POPs?

If your CDN does not offer prefetching, set up an origin shield to help offload your origin. Next, figure out the IP addresses of the shield POP and write a 'prefetch script' that requests each of the files you want to prefetch from those shield POP IPs, forcing the shield POP to fetch from origin and store in cache.

CDNs and Prefetch

  • Available/supported = Yes
  • Partially = Sort of/partially
  • Not available/supported = No
  • Extra costs = Extra costs
  • Unknown = Unknown
CDN Instant Free API All POPs
QUANTIL Not available/supported Not available/supported Not available/supported Not available/supported
Limelight More info Unknown Extra costs Unknown Unknown
StackPath Not available/supported Not available/supported Not available/supported Not available/supported
CDN77 More info Available/supported Available/supported Available/supported Available/supported
Fastly Not available/supported Not available/supported Not available/supported Not available/supported
CDNetworks Not available/supported Not available/supported Not available/supported Not available/supported
Level 3 Not available/supported Not available/supported Not available/supported Not available/supported
Incapsula Not available/supported Not available/supported Not available/supported Not available/supported
Cloudflare Not available/supported Not available/supported Not available/supported Not available/supported
Verizon Digital Media Services More info Partially Partially Available/supported Available/supported
CloudFront Not available/supported Not available/supported Not available/supported Not available/supported
CacheFly Not available/supported Not available/supported Not available/supported Not available/supported
Akamai More info Unknown Unknown Not available/supported Unknown
BelugaCDN Not available/supported Not available/supported Not available/supported Not available/supported
CDNvideo Unknown Unknown Available/supported Unknown
Tata Communications Not available/supported Not available/supported Not available/supported Not available/supported
CDNs missing in this table? That is because we don't have the relevant info

More info per CDN

Verizon Digital Media Services

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.

Akamai

Akamai does not provide prefetching functionality, but the following two community articles contain useful info: Content Pre-loading / pre-warming at Akamai. Media Content Pre-loading / pre-warming at Akamai. Both articles are a bit old though (2015).

Limelight

Limelight has a product/feature called Intelligent Ingest that allows for automated upload into Limelight's Origin Storage Services.

CDN77

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?


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