I'm currently looking into redis for similar needs. I'd be using it from perl and wondered how will it would scale... (IIRC (from people I know who have worked there) youporn/pornhub runs on Catalyst, an MVC-based web framework written in perl.)
Their certainly regarded as probably being one of the busiest Catalyst sites and they were employing Perl/Catalyst developers back in 2009: http://news.ycombinator.com/item?id=565152
