The Rust SDK does not currently use the CRT under the hood. The CRT is a high performance C-Library for fast HTTP connections (and a lot more). For S3, there i

The Rust SDK does not currently use the CRT under the hood. The CRT is a high performance C-Library for fast HTTP connections (and a lot more). For S3, there is a meta-layer that interceps requests to S3 and converts them into ranged-gets and multipart uploads for parallelization. It's quite complex and can also use significantly more memory, but it does allow for *much* faster uploads and downloads in some circumstances.