ledge

Ledge aims to be an RFC compliant HTTP reverse proxy cache wherever possible, providing a fast and robust alternative to Squid / Varnish etc.

Moreover, it is particularly suited so applications where the origin is expensive or distant, making it desirable to serve from cache as optimistically as possible. For example, using ESI to separate page fragments where their TTL differs, serving stale content whilst revalidating in the background, collapsing concurrent similar upstream requests, dynamically modifying the cache key specification, and automatically revalidating content with a PURGE API.