I understood your phrase "the major cause" to mean majority reason, that couldn't be true since the remaining difference is greater. If you meant something diff

I understood your phrase "the major cause" to mean majority reason, that couldn't be true since the remaining difference is greater. If you meant something different than that, then I misunderstood you. We both agree that the remainder of the performance (the bulk of it) must come from other reasons than parallelism. As well as your suggestions (doing less work, choosing the right data structures) - I would also propose (A) no V8 JIT warmup time (B) no need for fstat on many node_modules files (C) fewer AST passes (D) possibility of value struct types => less boxing => lower GC pressure (E) less dynamism/no plugin architecture.