This question is going to make me sound like a jerk, but why do you want to write your back-end in JS? Deno looks like a great improvement over node.js, but I don't feel compelled to use it. It seems like people jumped to node based on some performance promises that didn't really pay off (IMO). And since then, we have newer options like Rust, Go, and Elixir as performant back-end options, and even older choices like…
(but still: don't underestimate the raw performance of V8, for many things it's definitely good enough)