I posted and idea last week to Ideas and Feature Requests: "Finer grained control on caching" (http://forum.nginx.org/read.php?10,217748), but since I'm new to this forum/mailing list I have no idea if anybody saw this.

I want to find out if this is an acceptable feature request and if anybody else sees the benefits of this.

Short summary:
Add a new directive fastcgi_cache_key_suffix
Construct the caching filename like this md5(fastcgi_cache_key) . '_' . fastcgi_cache_key_suffix