Unplanned? Probably. But maybe it's not as a dire as you think? Azure Active Directory (auth as a service) went down for a while, globally, and life went on. Same with GCP and occasionally AWS[1]

I'm not saying there's no downside, I'm asking against the downside of engineering cost. And that itself carries risk of failure when you go live. It's not guaranteed.

[1] AWS is so ubiquitous though, that half the internet would be affected so it makes it less individually noticeable.