Memcached/other key-value engine isolation

Question

I have a bunch of web servers(frontends) behind balancer. Each apache process runs with it's own user for every virtualhost. Code that apache runs is PHP and it's not trusted code. I need to have shared (between web servers) session storage and limit user(vhost) to only access it's session storage. So I want to avoid one tenant to be able to purge or corrupt memcached stored data. So I basically looking for solution to authenticate users + create private buckets. I know there is always MySQL way avaliable but I want to avoid performance penalty introduced by SQL layer.

Any solution in your mind so far?

Answer 1

I found product called CouchBase which fully comply with my requirements. It has buckets along with memcache caching layer and access protocol. It has SASL authentication and a bonus of load balancing and fail tolerance.