Your correct, but this is combatted in practice through UX usually. Doing work in the background, doing retry w/ decay, bubbling up things that didn't go well

Your correct, but this is combatted in practice through UX usually. Doing work in the background, doing retry w/ decay, bubbling up things that didn't go well to the user at the right time, etc. For a client to just spam 300 requests the moment there is a hiccup that is generally not good. At scale its indistinguishable from a DDOS (been there, hah!). Also for it to be that jarring we are talking about a failure at the exact moment you are using the data-heavy app, and not 1 minute before. Every time you go to use the app its likely the dns is re-queried. So, at the end of the day if you have a mission critical thing running where you need to try very hard and can't tolerate 60 seconds of failure, you would bake multiple paths to a backend in the client configuration at some point. So the client would know if backend A is down it can do client side failover to backend B. Sometimes this technique is used in conjunction with a highly fault tolerant server stuff, and not as a replacement for it.