I think people forget that those large environments are there for a reason. To make sure the service stays up in the face of problems outside your own control.
https://hn.algolia.com/?dateRange=all&page=0&prefix=false&qu...
My entire point is that you have no redundancy in your system and you also aren’t big enough to have any pull with the vendors who can fix these types of outages so you’re basically at the mercy of your providers with no recourse.
That’s why these systems are built the way they are.
And generally four nines is considered the gold standard these days. I can tell you for sure that both Netflix and Ebay would lose money anytime they drop below four nines because I have at some point been responsible for both. You’re correct that Reddit has a lot more leeway and outage time before they start losing money but not that much leeway.
"What are you optimizing for?" is always an important question, as is "The Five Whys."
Over multiple ISPs, so far internet outages for more then a few minutes is very rare (though the few minutes would make me not want to host something requiring high availability; and a cut cable is really annoying because there simply is no quick fix), power outages even rares, I experienced 3 in 40 years, and the longest was 6 hours.
Ignoring for now how you are synchronizing the database and filesystem, and how doing so may well result in your duplicate experiencing the same failure as the original, you can maybe recover from a small class of availability issues that could knock you out of an SLA.
But that assumes you can get online and can fully orchestrate the transition within less than 53 minutes of it starting. Including the time you took to become aware of it. And including the time to diagnose and decide that a switchover would resolve the problem. Including the time it takes for DNS caches to expire and point to the new host. Including the DNS caches which may ignore your TTL. And including all these things again when you switch back.
And assuming, of course, that it doesn't happen again for a whole year.
Built how? Because I can state with confidence that I have cleaned up a ton of failed upgrades/zombie terraform deploys of these serverless kubernetes wonders that followed every best practice under the sun, and these things are not really considered even moderately reliable (as designed by imperfect mortals under real world conditions), meanwhile professionally, people who stand to lose a lot of money should their systems go down generally operate systems whose architectures were designed decades ago, are generally horizontally scaled monoliths, and are extremely conservative in software choice.
Also downtime often is no biggie, as long as it's planned and or don't lose (too much) customer critical data.
Like nodobody cares if your test db cluster goes down for the weekend. We even shut down our db instances to save money.
Even if a solar flare takes out an entire continent or two I think it's safe to say that the bittorrent network will still be running in some form. Can you be so certain about any given SaaS product?
(I hope you'll agree that the middle east outage is a true outlier)