Greg Wilkins has an impressive 'Web pedigree’; he is the founder and lead developer of Jetty. Greg is a long-time member of the Servlet Expert Group; he is also a member of the IETF HTTP/2 working group member, etc.!
During his JavaOne session, Greg gave a deep technical overview on Asynchronous IO using the Servlet API. Greg starts by explaining what asynchronous means in the context of a Servlet. He then goes and explains the Servlet 3.0 asynchronicity support. The rest of the talk is then spent on the Servlet 3.1 API and how to write effective asynchronous servlets (and how the inner-working of the API). Greg also shares some of the motivations behind the Servlet 3.1 API and the technical choices behind it. Not only that, Greg is also talking about some 'potential more obvious technical options' and why those options were not selected at the end.
This technical session provides different angles (e.g. Servlet API explanations, some deep technical points such as some of the Jetty implementation details but also best practices advices, etc.). Overall this session is highly recommended for anyone who want to understand asynchronicity in the context of the Servlet API.
You can find Greg's slide here.