Cloudflare Cache Reserve FAQ & Answers

Cache Reserve (launched 2022, GA 2023) is Cloudflare's persistent edge caching service with guaranteed 30-day minimum retention period, designed to reduce origin egress costs for infrequently accessed content. Key difference from standard cache: Standard Cloudflare cache uses LRU (Least Recently Used) eviction - unpopular content purged in hours/days. Cache Reserve overrides LRU, guarantees 30-day retention regardless of cache popularity, origin cache headers (Cache-Control, Expires), or edge cache eviction policies. Content stored in Cache Reserve remains cached for at least 30 days. Primary benefit: reduces origin egress costs 95%+ for cold/long-tail content by serving from Cloudflare's persistent storage instead of repeatedly fetching from origin (AWS S3, CloudFront).

Cache Reserve two-tier caching architecture: (1) Standard edge cache - 330+ locations, serves hot content with <10ms latency (RAM-based, LRU eviction), (2) Cache Reserve tier - backed by Cloudflare R2 object storage, serves cold content with 50-100ms latency (persistent storage, guaranteed 30-day retention). Request flow: Edge cache miss → check Cache Reserve → fetch from origin only if both miss. Example: popular blog post stays in edge cache (<10ms response), unpopular post from 2 years ago stays in Cache Reserve (50-100ms response but still faster than origin), eliminates origin fetch saving egress costs. Cache Reserve respects cache-control: no-store (never caches sensitive content). Content automatically promoted to edge cache on access.

Use cases: (1) Archival content - old blog posts, documentation, legacy product pages rarely accessed but expensive to re-fetch, (2) Large media files - video libraries, software downloads, game assets (multi-GB files with high egress costs), (3) Long-tail content - 80/20 rule where 20% content gets 80% traffic, remaining 80% benefits from Cache Reserve, (4) Origin cost optimization - AWS S3/CloudFront egress costs $0.08-0.09/GB. Pricing (2025): $0.015/GB/month storage fee (competitive with R2), no data transfer fees between Cache Reserve and edge. Example savings: 10TB video library with 5% monthly access rate - Origin egress without Cache Reserve: 500GB × $0.09 = $45/month, with Cache Reserve: $0.015 × 10,000GB = $150/month storage, then ~$5/month egress (saves $40/month after 4 months). Best for websites with large content libraries, reducing AWS/GCP egress bills.

Configuration: Enable via Cloudflare dashboard (Cache Rules → Cache Reserve), specify eligible content by URL pattern, file extension, or custom logic in Cloudflare Workers. Example: cache all /static/* URLs or .mp4/.zip files in Cache Reserve. Limitations: (1) Enterprise-only feature (not available on Free/Pro plans), minimum commitment typically required, (2) Does not replace origin - still need origin server for cache misses, (3) 30-day guaranteed retention, but Cloudflare may keep content longer (not guaranteed beyond 30 days), (4) Cache Reserve respects cache-control: no-store (never caches), must have valid cache headers for content to be eligible. Critical: Cache Reserve does not cache if origin returns no-store or no-cache headers. Use Cache-Control: public, max-age=31536000 for static assets to enable caching.

Use Cache Reserve when: websites with large content libraries (news sites, streaming platforms, SaaS documentation, video hosting), reducing AWS/GCP egress bills (S3 transfer costs $0.08-0.09/GB), improving cache hit ratio from 70% to 95%+ (long-tail content), infrequently accessed but expensive-to-fetch content (archival data, legacy assets). ROI threshold: typically breaks even after 3-4 months of storage fees vs origin egress savings. Not for: (1) Frequently changing content - API responses, personalized pages, real-time data (defeats purpose of 30-day retention), (2) Small websites - <1TB total content (storage fees exceed savings), (3) Free/Pro Cloudflare plans - Enterprise-only feature, (4) Content requiring <50ms latency - Cache Reserve adds 50-100ms vs edge cache <10ms (use standard edge cache instead). Best practice: combine standard edge cache (hot content) + Cache Reserve (cold/long-tail) for optimal cost/performance.