[amortize]

> I also consider this a success story for Clojure.

It is a success story for Clojure, but this move is a big negative feedback for the language. A team starting out on an open-source project will be mighty reluctant to start it with Clojure; because it might get rewritten not so much into the future. That is not good news for Clojure

[fnordsensei]

If, five years (or what-have-you) down the line—when you've pretty much enumerated all use-cases for the project, solidified what it's supposed to do and how, learned from your mistakes, and so on—you can't come up with a better design, something is off. With all that knowledge, there should be plenty of space for performance optimizations and pruning of vestigial stuff for a non-trivial project.

As for switching to Java, that makes perfect sense to me if that is what the contributors prefer. If you're going to make a big rewrite, you might as well change the language to one you prefer when you have the opportunity.

As someone who spends 100% of dev time in Clojure, I'm quite happy to see this development. Dipping into Java isn't uncommon for optimizations in Clojure, so this is like someone taking the time to do a massive under-the-hood optimization from the point of view of a Clojure user. I doubt it changes the project's status much in the Clojure community. Perhaps it'll even see an uptake in use.

What it doesn't say much about is Java vs. Clojure in my opinion. Different contributors, with different amounts of pertinent knowledge, and years apart. I'm not sure how you would control for those variables in a comparison. It should be read more as, "we put in a heck of an effort to make this thing faster and more useful", and kudos for that.