>Done wrong, it would extend the FB outage longer.

Let's hope it's done wrong.

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...

Clients weren't getting NXDOMAIN, they were getting SERVFAIL because the nameservers were unreachable. These responses cannot be cached for more than 5 minutes [1].

[1] https://datatracker.ietf.org/doc/html/rfc2308#section-7.1

Yes, that's the point. If you're running a DNS server and being overwhelmed by this, you might have considered artificially injecting NXDOMAIN with a long cache value to get some relief. Which could extend the outage for FB.

Unless the operators were in direct contact with Facebook, it doesn't sound like a good idea. It's certainly not the job of the ISP to reduce an outage for FB. They also weren't sure if the outage would only be 5 minutes or 5 hours. Instead, ISPs should scale up and handle DNS traffic for outages like this. In this case, FB isn't the only company to learn a lesson or two around failure modes and how to improve in the future.

The point isn't reducing an outage for FB, it would actually extend the outage for some. The point would be to help give some relief to a DNS server you're running that's overloaded due to the FB outage...during the "crisis". Yes, of course, better planning ahead of time is nice. In any case, I didn't suggest doing this. I wondered if it was happening.

I think you missed the idea that the FB outage created a really heavy DNS load on other people's DNS servers.

No, I didn't miss the idea (and it's not an idea, it really happened.) I believe you're mistaking the role of the resolver operator and whether or not they should be manipulating client queries/responses without the user knowing. An NXDOMAIN response does not match the conditions, and shouldn't be used just to manipulate the clients.