Cloudflare Launches Cache Response Rules for Post-Origin Cache Control

New Cache Control Capabilities

Cloudflare has launched Cache Response Rules, a new rules engine designed to operate after an origin server responds but before the content is written to Cloudflare's cache. This expands upon previous Cache Rules, which only operated on request attributes. The new response phase allows for evaluation and modification of origin responses before they are stored in the cache.

Enhanced Cache Management

Cache Response Rules enable users to modify Cache-Control directives, manage cache tags, and strip headers such as Set-Cookie, ETag, and Last-Modified. This functionality provides more granular control over cache behavior and can significantly improve cache hit rates. The primary benefit is that these changes can be implemented without altering the origin application, which simplifies CDN migrations and ongoing maintenance.

Addressing Caching Challenges

The introduction of Cache Response Rules addresses common issues where headers like Set-Cookie or incorrect Cache-Control directives prevent assets from being cached effectively. Such scenarios can lead to increased origin bandwidth usage, degraded performance, and higher infrastructure costs. By allowing these headers to be modified or removed at the Cloudflare edge, the new rules help ensure that content that should be cached is indeed cached.

Operational Flow

Caching decisions now involve two phases. Request-time rules determine how content is looked up in the cache before contacting the origin. Cache Response Rules then execute after Cloudflare receives a response from the origin but before that response is stored in the cache. This allows for dynamic modification of cache-related headers and management of cache tags, ensuring optimal caching behavior.