I keep finding 'fixed' hosting plans. Is there a 'variable' hosting plan that would 'Hug-O-Death'-proof my website (i.e. being able to handle large volumes of sudden traffic)?

I really want to be able to do this on the off chance something I make goes viral, but every plan I've seen so far is just a fixed amount of storage/bandwidth for a certain rate.

I don't even know how much bandwidth I'm gonna need, so even between those plans I'm at a loss for what to pick.

Is there some term I'm missing for the utility-like "pay-by-the-use" kind of hosting plan, or do those just not exist? :(