By default, it seems that if you enable CDN that this plugin assumes the files you selected to be on the CDN are available on the CDN. This works for the most part, however when I have a client uploading new images, I do not want to have them go to the performance tab every time to upload changes to the CDN.
I notice there is an "Automatically Upload Changes" option, however this currently defaults to 1 hour. Cranking that up to every minute would solve my problem, however sometimes there will be weeks or months without ever uploading a new image, and a lot of resources are wasted checking for new files every minute.
Is there a way to have the plugin do a quick check to see if the image exists, and if not, fall back to the local copy? Can this be done in htaccess?