For the simplest benchmarks the performance disparity might come down to the difference between JavaScriptCore (which Bun uses) and V8 (which Node uses), but for anything non-trivial there's a significant amount of overhead introduced by the Node runtime.

Someone wrote a barebones V8 wrapper called Just Js, which is based on V8 just like Node, but it crushed Node in the Techempower benchmarks [1].

[1] https://www.techempower.com/benchmarks/#section=data-r21&tes...