Cloudflare

Cache Reserve Gotchas

Common Errors

"Assets Not Being Cached in Cache Reserve"

Cause: Asset is not cacheable, TTL < 10 hours, Content-Length header missing, or blocking headers present (Set-Cookie, Vary: *) Solution: Ensure minimum TTL of 10+ hours (Cache-Control: public, max-age=36000), add Content-Length header, remove Set-Cookie header, and set Vary: Accept-Encoding (not *)

"Range Requests Not Working" (Video Seeking Fails)

Cause: Cache Reserve does NOT support range requests (HTTP 206 Partial Content) Solution: Range requests bypass Cache Reserve entirely. For video streaming with seeking:

• Use edge cache only (shorter TTLs)

• Consider R2 with direct access for range-heavy workloads

• Accept that seekable content won't benefit from Cache Reserve persistence

"Origin Bandwidth Higher Than Expected"

Cause: Cache Reserve fetches uncompressed content from origin, even though it serves compressed to visitors Solution:

• If origin charges by bandwidth, factor in uncompressed transfer costs

• Cache Reserve compresses for visitors automatically (saves visitor bandwidth)

• Compare: origin egress savings vs higher uncompressed fetch costs

"Cloudflare Images Not Caching with Cache Reserve"

Cause: Cloudflare Images with Vary: Accept header (format negotiation) is incompatible with Cache Reserve Solution:

• Cache Reserve silently skips images with Vary for format negotiation

• Original images (non-transformed) may still be eligible

• Use Cloudflare Images variants or edge cache for transformed images

"High Class A Operations Costs"

Cause: Frequent cache misses, short TTLs, or frequent revalidation Solution: Increase TTL for stable content (24+ hours), enable Tiered Cache to reduce direct Cache Reserve misses, or use stale-while-revalidate

"Purge Not Working as Expected"

Cause: Purge by tag only triggers revalidation but doesn't remove from Cache Reserve storage Solution: Use purge by URL for immediate removal, or disable Cache Reserve then clear all data for complete removal

"O2O (Orange-to-Orange) Assets Not Caching"

Cause: Orange-to-Orange (proxied zone requesting another proxied zone on Cloudflare) bypasses Cache Reserve Solution:

• What is O2O: Zone A (proxied) → Zone B (proxied), both on Cloudflare

• Detection: Check cf-cache-status for BYPASS and review request path

• Workaround: Use R2 or direct origin access instead of O2O proxy chains

"Cache Reserve must be OFF before clearing data"

Cause: Attempting to clear Cache Reserve data while it's still enabled Solution: Disable Cache Reserve first, wait briefly for propagation (5s), then clear data (can take up to 24 hours)

Limits

Additional Resources

• Official Docs: https://developers.cloudflare.com/cache/advanced-configuration/cache-reserve/

• API Reference: https://developers.cloudflare.com/api/resources/cache/subresources/cache_reserve/

• Cache Rules: https://developers.cloudflare.com/cache/how-to/cache-rules/

• Workers Cache API: https://developers.cloudflare.com/workers/runtime-apis/cache/

• R2 Documentation: https://developers.cloudflare.com/r2/

• Smart Shield: https://developers.cloudflare.com/smart-shield/

• Tiered Cache: https://developers.cloudflare.com/cache/how-to/tiered-cache/

Troubleshooting Flowchart

Asset not caching in Cache Reserve?

1. Is Cache Reserve enabled for zone?
   → No: Enable via Dashboard or API
   → Yes: Continue to step 2

2. Is Tiered Cache enabled?
   → No: Enable Tiered Cache (required!)
   → Yes: Continue to step 3

3. Does asset have TTL ≥ 10 hours?
   → No: Increase via Cache Rules (edge_ttl override)
   → Yes: Continue to step 4

4. Is Content-Length header present?
   → No: Fix origin to include Content-Length
   → Yes: Continue to step 5

5. Is Set-Cookie header present?
   → Yes: Remove Set-Cookie or scope appropriately
   → No: Continue to step 6

6. Is Vary header set to *?
   → Yes: Change to specific value (e.g., Accept-Encoding)
   → No: Continue to step 7

7. Is this a range request?
   → Yes: Range requests bypass Cache Reserve (not supported)
   → No: Continue to step 8

8. Is this an O2O (Orange-to-Orange) request?
   → Yes: O2O bypasses Cache Reserve
   → No: Continue to step 9

9. Check Logpush CacheReserveUsed field
   → Filter logs to see if assets ever hit Cache Reserve
   → Verify cf-cache-status header (should be HIT after first request)

See Also

• README - Overview and core concepts

• Configuration - Setup and Cache Rules

• API Reference - Purging and monitoring

• Patterns - Best practices and optimization