As vladd pointed out, one should be comparing Rhino with V8, especially since there are other server side JavaScript platforms running on V8 like http://www.aks

As vladd pointed out, one should be comparing Rhino with V8, especially since there are other server side JavaScript platforms running on V8 like http://www.akshell.com http://www.akshell.com Apparently the new Dynamic Invoke feature in Java 7 has resulted in significant performance improvements in the latest patches of Rhino, but it still lags behind V8: http://twitter.com/hannesw/status/39677300169515008 http://twitter.com/hannesw/status/39677300169515008 That being said, performance isn't the only factor, since Rhino offers the ability to utilize the wealth of well designed and production ready Java libraries, a much better garbage collector and ability to use more than 2GB of heap. However, these advantages that Rhino has over V8 will be eroded with time as more and more of these libraries are reimplemented in pure JavaScript. A much more interesting question is whether asynchronous I/O will trump synchronous I/O for web app development. At Akshell we believe that the concrete advantages that synchronous I/O offers in terms of ease of development outweigh the potential benefits of increased performance offered by asynchronous I/O.