Caching recommendations for Acquia Cloud Edge

Acquia recommends the following defaults for page caching rules in Acquia Cloud Edge CDN:

  • Edge Cache TTL (Time To Live) – 1 minute
  • Browser Cache TTL – 1 minute, or the same value as Edge Cache TTL

Occasionally, an application may require a shorter Edge Cache TTL lifetime. If you reduce the amount of your Edge Cache TTL, be sure to change the Browser Cache TTL to the same value.

You should also configure Page Cache Maximum Age (the amount of time assets are cached in Varnish® and Drupal) to your desired value, typically 30 minutes to one day. Acquia Cloud Edge CDN will contact Varnish only once per minute for updated copies of that asset.

Updating cached content before expiration

If your content or assets have changed at origin (in your Drupal website), and you need to update the cached copies of these assets before the Page Cache Maximum Age expiration date, Acquia recommends that you use the Acquia Purge module.

When configured properly, the Acquia Purge module will cause content updates to purge selected portions of Varnish cache. The next time Acquia Cloud Edge CDN requests the asset from Varnish, it will receive the newly-updated content.

Important

Due to API limitations that can prevent website visitors from viewing updates to content, Acquia does not recommend using the CloudFlare Purge (cfpurge) module.

Cache tags on Acquia Cloud Edge

When purging caches on Acquia Cloud Edge CDN using the API or the dashboard, the Cache-Tag header (including whitespace and commas) must not exceed 255 bytes in total length after the header field name. If the supplied Cache-Tag header exceeds 255 bytes in length, only the tags in the first 255 bytes will be purged.

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