I think if you want to do web dev backend with Rust (or C++ or any bare metal lang), you should do it behind a RPC framework (Thrift, gRPC) if only for security

I think if you want to do web dev backend with Rust (or C++ or any bare metal lang), you should do it behind a RPC framework (Thrift, gRPC) if only for security purposes. But it's also way more convenient. There's no need to have your core business logic also become entangled with a web server unless the networking minutiae is relevant. There are too many things that could go wrong on a public-facing endpoint to trust the runtime of something you are essentially rolling on your own if you use Rust, C++, C, etc.