> This being written in Rust tells me it's probably going to be fast/lightweight. Go would be a similar expectation. If it's written in Rails I'd have different expectations. Python or Node might fall somewhere in the middle.

Which is exactly why the language doesn't matter. It being written in rust doesn't tell you anything, and serves only to evoke some predisposition you have for rust. There's nothing in rust that stops users from writing horrible algorithms. This reddit front end could send separate requests for every letter it loads for all you know.