Yeah; but at the same time when you're building and scaling an app you run into all sorts of issues like this. JRuby is almost a platform of its own: you get the scalability and benefits of the JVM with the flexibility of Ruby. IMO it's a decision you make pretty early in the product lifecycle. If you're already on Rails, there are other solutions that give you many of the same benefits with an easier migration path (i.e. app containers like Docker).