This kind of attitude is how we get bloated Electron apps that HN (including me) loves to complain about. Speed should be a first class consideration, not something to throw away for later.

> No one is gonna be able to tell Rust vs Go in a web API

Debatable, Discord moved from Go to Rust [0] because they were getting latency and CPU spikes from Go's GC, and I'd assume that's the same with any GC language because, well, the GC has to run sometime. Now you might say that we're not all Discord scale, to which I'd say, like above, there are benefits to Rust that are more than just speed. Cargo alone is nigh unbeatable compared to some other languages. I was trying to get Python to work the other day and was pulling my hair out over venv, virtualenv, pip, conda etc.

[0] https://news.ycombinator.com/item?id=26227339

It matters to whoever is paying for compute. If you get some other benefit, it may be a worthwhile tradeoff, but it always matters.

Speed equals money. The same app running at twice the speed uses half the compute resources. You may also gain a lot of simplicity if you don't need to distribute your architecture so early on.