From the post:
Riak is a key-value based NoSQL database that can be used to store user session related data. Andy Gross from Basho Technologies recently spoke at QCon SF 2011 Conference about Riak use cases. InfoQ spoke with Andy and Mark Phillips (Community Manager) about Riak database features and best practices when using Riak.
Not a lot of technical detail but enough to get a feel for whether you want/need to learn more about Riak.