aleph is a new ultra-thin wrapper around the popular Netty framework by Zachary Tellman.
In Clojure we don't need to use callbacks. This means for common things like talking to databases, we don't need them to have asynchronous interfaces. That's because we have really fantastic primitives in the language itself for dealing with concurrency. This code runs twice as fast as the Node.js counterpart - probably due to the excellent perf of Clojure coupled with leveraging multiple cores.