Couple points (I've worked on app servers): 1- This is exactly how we should all be thinking about server engineering moving forward, as we aim to drastically reduce carbon footprint within 11 years. Efficiencies at the language level are one of biggest bangs for buck here. Just by redeploying, you can reduce energy consumption by perhaps double digits. Imagine how hard that is to do at the hardware or energy farm le…
I don't think carbon footprint is the be-all end-all you suggest. In a startup that has yet to scale, trading off efficiency for, say, flexibility, safety, or expressiveness may have minimal carbon impact but major benefit for your business. After all, few here will defend the choice of C for web service development these days.
If it were up to me, no matter the energy consumption, a piece of software in that realm should be proven correct (both crash-free and doing what the specification says).