The problem is more about latency, not so much bandwidth. Also, not everyone has a good connection.
Cache only works the second time the user comes to your page. By definition, every user will experience slow loading the first time.
That said, it probably depends on your use case if it is worth bothering with a CDN or not.
Re:How to deploy a React app for free
by thomaslord on Wednesday August 19, 2020 @09:55AM
(#24210367)
In the case you mentioned (top of HN with 10,000 visitors), each user would be loading the full webapp for the first time, so I think caching would be mostly irrelevant.
And downloads shouldn't take too long. Basic 1Gbit connections give you 100Mbyte per second, 10M per 100mils. A landing page should be doable in 10M, and then there is at least one second left to load the rest of the page before the user can react and make a choice.