"without writing to disk" This is a valid concern and a good enough reason to have such a library. I've written a similar thing for uploading large files to S3

"without writing to disk" This is a valid concern and a good enough reason to have such a library. I've written a similar thing for uploading large files to S3 (via Django) by streaming them without the file ever touching the file system (S3ChunkUploader). The reason was the large files were deemed security-sensitive and the containers were limited to 2GB in disk space. Just uploading 4 500MB files at the same time would be an attack vector.