Transpiling TS to JS on startup does incur a cold start penalty, you can minimize it by using the `--no-check` option to transpile with SWC instead of TSC but it's still there. On subsequent runs though, it'll start up instantly because the JS is cached locally after transpiling (you can even trigger this step yourself with `deno cache`)

Beyond that, you still have the v8 engine running the JS, so yeah in most cases performance will be pretty much what you can expect from Node _except_ with regards to anything that reaches out of the sandbox (like filesystem or network access). These APIs are handled completely differently outside of v8, with Deno relying on a lot of Rust packages, and Promise-based APIs all the way down. For the builtin HTTP server for example you can expect higher throughput from Deno. Tail latencies also tend to be better with Deno.

You're not immediately going to get "blazing fast, native speeds" but you can get some nice optimizations.

> These APIs are handled completely differently outside of v8, with Deno relying on a lot of Rust packages

Very cool, thanks for the detailed answer.