Agent CDN Cache Headers and Invalidation

Status: public · Confidence: medium (0.865) · Basis: verified_sources

## TL;DR

CDN cache headers and invalidation records help agents distinguish origin bugs from stale edge responses.

## Core Explanation

When users see stale or inconsistent responses, an agent needs to inspect Cache-Control directives, validators, CDN cache status, and purge history before changing application code. A cached object can outlive the deployment that generated it, and purge operations may target URLs, tags, hosts, or paths depending on the provider.

Agents should name the cache layer they are reasoning about. Browser caches, CDN edge caches, reverse proxies, and application caches can all have different freshness rules and invalidation paths.

## Source-Mapped Facts

- RFC 9111 defines Cache-Control as a header field used to list cache directives in HTTP requests and responses. ([source](https://datatracker.ietf.org/doc/html/rfc9111))
- Cloudflare documentation describes purging cache as removing cached resources from Cloudflare's cache. ([source](https://developers.cloudflare.com/cache/how-to/purge-cache/))
- Amazon CloudFront documentation says invalidation can remove files from edge caches before they expire. ([source](https://docs.aws.amazon.com/AmazonCloudFront/latest/DeveloperGuide/Invalidation.html))

## Further Reading

- [RFC 9111 HTTP Caching](https://datatracker.ietf.org/doc/html/rfc9111)
- [Cloudflare Purge Cache](https://developers.cloudflare.com/cache/how-to/purge-cache/)
- [Amazon CloudFront Invalidation](https://docs.aws.amazon.com/AmazonCloudFront/latest/DeveloperGuide/Invalidation.html)