I don't quite understand this from the documentation I'm reading. Doesn't high fault tolerance require automatic failover of some sort that goes beyond broadca

I don't quite understand this from the documentation I'm reading. Doesn't high fault tolerance require automatic failover of some sort that goes beyond broadcasting the messages to all Hooks? For instance, if you want to send an SMS robustly are you supposed to have multiple SMS listeners? And if so, how do you avoid sending multiple messages without some sort of ACK or message queue?