Emil Eifrem explains graph databases, what domains they fit well, and the state of Neo4j. Also: how graph databases stack up against RDBMs.
Justin Sheehy explains how Riak was created with ideas from Amazon's Dynamo paper, Riak features and how Riak compares to other NoSQL solutions.
Ilya Grigorik discusses his company's PostRank algorithm for tracking reader engagement with content. Also: his experience scaling MySQL, Tokyo Cabinet, Ruby HTTP libs, Solr, Amazon EC2 and more.
Dan Pritchett gives us an inside look into the decisions behind on of the largest scale architectures in the world: eBay. In explaining how the scale of eBay turns simple requirements a complex engineering problem, he walks us through the technical and organizational challenges of managing eBay's architecture.