Firstly, I'm not solving anything. I'm explaining why fallback URLs are not equivalent to CDNs.
You don't use a CDN because your site doesn't work, you use it because it's faster.
Secondly, no, doing an occasional speed test, using data you'd be downloading anyway, then selecting an endpoint between speedtests does not increase bandwidth usage by 3x.
Some people use CDNs as regular static-site web hosts, or hosts of an SPA client JS blob when they have an otherwise-"serverless" architecture. CDNs are not always about serving large media assets.
Firstly, I'm not solving anything. I'm explaining why fallback URLs are not equivalent to CDNs.
You don't use a CDN because your site doesn't work, you use it because it's faster.
Secondly, no, doing an occasional speed test, using data you'd be downloading anyway, then selecting an endpoint between speedtests does not increase bandwidth usage by 3x.
Baffled.