Everything fails, we can argue the rate. But I would argue that understanding your constraints is better.

if you know that your secret storage system can't survive if a machine goes away: well, you wire redundant paths to the hardware and do memory mirroring and RAID the hell out of the disks. And if it fails you have a standby in place.

But if you use AWS Cognito.

And it goes down.

You're fucked mate.