Troubleshooting Asset Caching Issues with Fastly and Cloudflare in AEM as a Cloud Service

When using Adobe Experience Manager (AEM) as a Cloud Service in conjunction with both Fastly (Adobe’s CDN) and Cloudflare (customer-managed CDN), caching issues—especially with static assets like PDFs—can become tricky to debug. 

One way to identify which CDN is serving the content is by reviewing response headers:

•    x-served-by: Indicates the response was served by Adobe’s Fastly CDN.
•    cf-ray: Identifies the response as coming from Cloudflare.

If you’re experiencing stale content being delivered (such as outdated PDFs), several potential causes and solutions should be considered.
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Possible Causes of Stale Content

1. Long TTL (Time to Live) Settings
   A high TTL on either CDN can result in outdated content being served for an extended period.
2. Improper Cache Invalidation
   If cache purging isn’t triggered after content updates, the old versions may persist in cache.
3. Lack of Versioning in URLs
   URLs for assets (like PDFs) without a versioning parameter or hash will not prompt the CDN to fetch new versions after updates.

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Next Steps for Resolution
 

To resolve or mitigate the caching issue, follow these recommended steps:

1. Check TTL Settings in Cloudflare
   Review cache-control settings for the affected assets. Ensure the TTL is appropriate for how often the content changes.
2. Manually Purge the Cache
   As a short-term fix, manually purge the specific asset (e.g., the outdated PDF) from Cloudflare’s cache. Confirm whether the new version is served afterward.
3. Automate Cache Invalidation
   Set up an automated cache purge process that triggers when content is published or updated in AEM. This helps avoid stale content going forward.
4. Inspect CDN Headers
   Ensure headers like Cache-Control, ETag, and Last-Modified are correctly configured. These headers help CDNs determine when content should be refreshed.

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Additional Configuration Tips

 
If applicable, also consider the following optimizations:

•    Shorten Cloudflare TTLs for specific content types like PDFs or other assets that change frequently.
•    Automate Cache Purging via API
Use Cloudflare’s API or webhooks to automatically clear cache for updated content.
•    Implement URL Versioning
Append a query string (e.g., ?v=2) or use a unique filename each time content is updated.
•    Integrate CDN Logic into AEM Workflow
Ensure the AEM publishing process includes steps to communicate with the Cloudflare API for cache control.
•    Enable Monitoring and Logging
Track cache hits/misses and set up alerting to proactively identify caching issues before they impact end users.
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Still Facing Issues?
After implementing the above steps, verify whether the issue has been resolved. If problems persist, it’s advisable to contact Cloudflare support directly to further investigate potential misconfigurations or unexpected caching behaviors on their end.