Apache2 mod_rewrite S3 file upload request body buffer

Question

I'm currently uploading a file directly to my S3 instance using the mod_rewrite to proxy the file upload from my Apache2 web server directly to my S3 instance.

RewriteCond %{REQUEST_METHOD} =PUT
RewriteRule ^/(.*)/(.*) https://$1.s3-host.com/$2 [P,NE]

Using the above approach my files upload speed is very fast, which leads me to question the number of bytes my server is reading into memory for each request. I haven't had much luck finding any information in the docs about proxy request buffer sizes, so I thought I'd try my luck here.

https://httpd.apache.org/docs/2.4/mod/mod_rewrite.html