Servlet 3.1 is a relatively minor release slated for Java EE 7. However, the Java EE foundational API still contains some very important changes, especially for folks building on the Servlet API. One such feature is the newly added support for non-blocking I/O to empower low-latency, high throughput applications, protocols and web frameworks.
Servlet 3.1 co-spec lead Shing Wai Chan shows you how in a recent code example driven post. Incidentally, Servlet 3.1 recently had it's final release. You can now check out the official specification yourself. You can also try the API out with a GlassFish promoted build.