Not sure at this point if this is an issue, or more of a documentation matter.
After enabling s3fs, we were having problems with thumbnails being generated for the Media module's Media Browser and for the Focal Point module. Both of them rely on Ajax/JavaScript to render the thumbnails on the fly.
After a bunch of investigation, we found the problem was a section of our Nginx configuration, specifically this code:
location ~* \.(js|css|png|jpg|jpeg|gif|ico)$ {
expires max;
log_not_found off;
}
This is used to not log image 404 errors to Nginx. However, it seems as though when image derivatives need to be generated by s3fs via Ajax/JavaScript, it causes the image itself to return a 404. Once the the code was commented out, the thumbnails started reappearing.
I'm certainly not an Nginx expert, but I'm guessing this might be due to some type of permissions issue. Just wanted to post in case others have insight or have run into a similar problem.