Your async container still can be useful, since you can have worker threads executing blocking operations. This works fine as long as your JDBC queries are fast

Your async container still can be useful, since you can have worker threads executing blocking operations. This works fine as long as your JDBC queries are fast enough to feed the event loop without creating tons of threads. What async containers like Netty (and by proxy, Vert.x) solve is high-latency cases like long polling and file upload/download. Netty for one does have support for zero-copy file transfers: http://docs.jboss.org/netty/3.2/xref/org/jboss/netty/example/http/file/HttpStaticFileServerHandler.html#80 http://docs.jboss.org/netty/3.2/xref/org/jboss/netty/example... In my experience, these are a small percentage of cases so the majority of the app can use blocking I/O -- even long-polling code, as long as you are using the async framework for the client connection.