Use direct downloads.tryton.org instead of CDN
I have setup a custom theme thanks to fancyindex on the nginx server (which works better for mobile), see https://downloads.tryton.org/ But in order to still reduce the server load, the download of binary files are redirected to the CDN. Because KeyCDN does not allow to customize the listing and advise to not activate the feature, it is better to serve the index pages ourselves.
The only drawback is that we could display a file that has not yet been uploaded to the CDN. But this is at most a delay of 1 day.