We are, depending on how you define "serious". The Rust usage is for our products as a company which largely target somewhat niche type of US companies. I can't

We are, depending on how you define "serious". The Rust usage is for our products as a company which largely target somewhat niche type of US companies. I can't speak much on it, but I do consider it "serious" because of the amount of money that flows through our product. However the corporate users are far far less than 100k. I chose Rust because 1. I enjoy the hell out of it; I feel productive and safe in the language. 2. Some services within our infra have tight memory requirements and I was having difficulty feeling confident on handling these requirements in Go. So if you're asking merely for concurrent traffic requests our uses are definitely not serious haha. If you're asking based on "professional" usage, our Rust usage is vital to tens of millions of USD. Not astronomical, but far more "real business" than a startup with 20 users haha :)