[toast0]

Function as a service isn't really what I'd call decentralized. It's centralized at the service provider. But, they mix your load in with everyone elses and they serve the load in many places (maybe geographically distributed is decentralized?).

But, voip.ms has points of presence all over and they were DDoSed effectively recently; distribution can often help, but it's not enough. If an attacker sends X gigabits of garbage at your San Jose PoP and disables it, your other PoPs will likely function, but if they send X/N gigabits at each of your N PoPs, that might be enough to disable all of them.

Using a large provider can help a lot though. Volumetric DDoS is 'solved' by having large pipes and discarding lots of traffic. And, where possible, getting upsteams to discard lots of traffic before it arrives on your network. Large providers have large pipes and good relations with their carriers. Smaller providers or DIY doesn't.