"A modern web application typically puts a web server like nginx in front and reverse-proxies to an application server written in another language like Ruby, Python, Go, or Rust. That always felt a bit strange to me: you essentially have two web servers, and one of them is also responsible for your business logic." -- Is the fundamental difference here that the business-logic binary is not always running but gets spun out with each request? This looks like a relatively minor thing, to be honest.