This outage also affected whatsapp, one of the most widely-used communication technologies in the world. It also almost caused me to be locked out of my apartment, were it not for random chance and the kindness of a stranger, but I’m glad that you can feel smugly superior about it

Just out of curiosity, and obviously if you can disclose... How does FB availability affect your ability to enter your apartment?

Not OP, but such ideas usually stem from a misunderstanding of root cause. Facebook inaccessibility likely exposed poor assumptions or other flaws in e.g. "smart" devices or workflows. Those poor assumptions or other flaws are likely what got OP locked out of his apartment when Facebook went down, not Facebook itself going down.

An apartment-complex entry app with Facebook login integration seems possible to me. That would be direct root cause.

https://developers.facebook.com/docs/facebook-login/

No, that would not be direct root cause. Direct root cause would be designing and implementing an apartment-complex entry app which depends on a working internet connection, battery, and network route to a single point of failure.

>but I’m glad that you can feel smugly superior about it

And I'm glad you can feel smug about combating smuggness, because obviously the consequences of some social media and chat apps being down can't be measured but by anecodotal stories of some unrelated issue like being locked out, not about their general societal impact, shady practices, contribution to disinformation and data mining, etc. Who's being self centered now?

If anything, the lesson here is to not depend on some single, centralized, channel, for such communications (e.g. to get your AirBnB key). Now I also feel smug for always giving 2-3 alternative ways in cases contacting someone/someone contacting me is crucial...

It's not like what the world lacks in 2021 is communication channels. One can use land phone, mobile phone, SMS, email, and 200 other alternative IM outlets...