Felix Enning pointed me again to an interesting question regarding mod_cache / mod_disk_cache:
The following situation was observed with Apache 2.0.54 (same applies to trunk): 1. A resource gets cached. 2. The original resource gets removed from the backend (e.g on a proxied webserver, on the local disk, wherever). 3. The client sents a request that forces the cache to revalidate this entry. 4. The 404 received from the backend is correctly passed back to the client by mod_cache. 5. The client sents a request that does NOT require the cache to revalidate this entry. 6. Cache delivers the old resource that had been cached before, instead of a 404. Is this behaviour intended and compliant with the RFC? The reason for this behaviour is that the remove_url function of mod_disk_cache is a dummy function (BTW: mod_mem_cache seems to really remove the cache entry in remove_url). If this behaviour is not intended I would have a look into this to create a patch. Regards Rüdiger