"As Dzuiba points out in his blog entry, pure JavaScript using Node.js does not take any advantage of multithreading; even in the presence of many concurrent requests, only one request can be serviced at a time by Node.js. Furthermore, the evaluation of the Fibonacci number in JavaScript takes almost 5 seconds, resulting in a constant 0.2 requests served per second, independent of the number of concurrent requests.

In comparison, Fabric Engine serves about 2.4 times the number of requests per second even when only only one request happens at once; this is because the calculation of the resulting Fibonacci number happens entirely in native, optimized machine code. More importantly, however, Fabric achieves near-linear scaling in the number of requests served per second up to the number of available cores. Once the number of concurrent requests surpasses the number of available cores, Fabric is able to serve the requests at the rate that varies between 3.48 and 3.81 requests per second, up to the end of the maximum tested 20 concurrent requests."

http://fabric-engine.com/2011/11/benchmark-node-js-fibonacci-server/