Following up my questions, I found a similar post that is that I’m asking in this post CloudFront not caching static files - #4 by Falco
Appreciated @Falco answer, in this Full site CDN setup, can I set the DISCOURSE_CDN_URL the same as DISCOURSE_HOSTNAME? As I assume the Full site CDN means CDN accelerate the URL of hostname which makes the DISCOURSE_CDN_URL the same as DISCOURSE_HOSTNAME. But here’s no a decent document about this in meta.