JVM startup time is slower than a lot of VMs, but it's not that slow. Write a hello world in Java and see how long it takes, I'd guess 100ms or so. Do the same in Clojure and you're looking at 3-4 seconds.

This is a good analysis of why Clojure startup is slow: http://nicholaskariniemi.github.io/2014/02/25/clojure-bootst...

This is why I think ClojureScript/Node should become the "default" environment for writing Clojure. It would open up Clojure to a new class of apps that are currently not practical.