The language doesn't matter much if you have memory-hungry workloads. Whether it's Rust or C or C#, you can write quite memory efficient code in either.

Most apps don't need much at run time though. There may be a big database somewhere, but the majority of SaaS apps are just some form of CRUD with a clever twist that might change the data occasionally, but doesn't use most of it when you render a page. The user data required for any given page is dwarfed by the memory required to run the language that converts the data to an HTML view.

For example, if you're rendering a user account page that has 100 data fields (name, address, etc), that's a few kilobytes at most. If your code is using Node of PHP you're probably using tens or hundreds of megabytes, possibly gigabytes, to turn that into a stream of HTML to send to the user.

I suspect using Claude to turn all the Node and PHP apps in the world to Rust or Go would massively reduce the necessity for huge datacentres using terabytes of memory.

Except that most of the time a workload is made memory-hungry by terrible technical decisions ("self-describing" text data encodings come to mind).

And Java? Language matters.