[robpalmer]

I'll offer one advantage we have nowadays, which is to permit writing and atomically deploying apps that have both client and server parts - there's no need to preserve compatibility or worry about coping with independent versions.

Our platform allows you to write this all inside one project - so the ability to use a single language across both sides helps app developers maintain mental flow and reduces context-switching. It's even better now that we have TypeScript to perform instant type-checking across the client-server boundary.

Gary Bernhardt shows off similar powers in his awesome video "End-to-End TypeScript: Database, Backend, API, and Frontend": https://www.youtube.com/watch?v=GrnBXhsr0ng

[hvidgaard]

I can see the benefit, but the context switch overhead of having two different languages in the same repository is not a productivity issue in my experience.