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Content Delivery Network (CDN)

  • Distribute cached static content
  • Example: movies, images, binary blobs, css, js, html, etc

  • Content is delivered from locations/servers very close to where the clients are

  • It's NOT applicable for dynamic content (e.g., user information), this info has to be retrieved from the database directly

CDN Servers

  • Often known as edge servers
  • They are located at different Points of Presence (PoP) at strategic locations

Pull strategy

  • The CDN will actively pull the asset from the original server when necessary
  • It's configured by setting a Time To Live (TTL) property for each asset
  • On the end of the TTL, the CDN checks with the server if the content has changed
  • If Not, renew the TTL with the existing asset

  • If Yes, download the new version and renew the TTL

  • Pros

  • Requires lower maintenance! (everything is taken care by the CDN provider)
  • Cons
  • The first users to require an asset (miss) will have a longer latency
  • The CDN may try to pull when the server is under maintenance

Push strategy

  • The server actively push a new asset version to the CDN

  • Pros

  • Reduces the traffic to the server
  • Less traffic to the server

Implementations

  • Cloudflare
  • Fastly
  • Akamai
  • AWS CloudFront
  • GCP CDN
  • Azure Content Delivery Network