Are you kidding me? Amazon, on their biggest day of the entire year (Prime Day), reached peak traffic of approximately 290m requests per minute through CloudFront. I would bet that loading a single Amazon page uses much less than a minute and serves more than 10 requests per page load.
If you're not going to be as big as the entirety of Amazon you don't need to serve 20 million concurrent users. Ever.
If you're not going to be as big as the entirety of Amazon you don't need to serve 20 million concurrent users. Ever.