Alex Miller is a respected Java concurrency and scalability enthusiast  who works on Terracotta, an open source, Java-based clustering system. In this talk with Andrew Glover, Alex demystifies Terracotta, explaining the programming magic that enables enterprise customers to run 50 to 100 JVMs on a single application server instance. Alex also talks about Terracotta's "sweet spot" -- storing session data off of the database -- and Terracotta 3.0, which promises new features that he says will eliminate certain scalability barriers.