Polyglot Ruby is invoked from Clojurescript which transpiles to JS which runs on GraalJS implementation running on GraalVM extension to the JVM?
this is both impressive and terrifying.
Actually, since this is Graal the Ruby implementation here is almost certainly https://github.com/oracle/truffleruby so you're invoking Ruby in the same compiler _and process space_ that underlies GraalJS (no transpilation to JS needed). That means the JVM can optimize calls between JS and Ruby (inlining JS values into Ruby method call sites, and vice versa).