> they went over how they handle a billion requests a day with mostly a Rails monolith
1 day has 246060=86400 seconds. 1bn/86400 is more than 10000 reqs/second, so each request has to be served in less than 100 us. According to [1], random access on an SSD is about 150us. This suggests to me it's likely that most of these are being served cached from a CDN. Are we supposed to be surprised that this can be done by a rails monolith? We don't know how many of those requests are actually hitting the rails app.
This is yet another instance of a phenomenon: When you have good outcomes and bad outcomes, and you take some preventative measures to reduce the likelihood of bad outcomes, as time goes by people start believing that the bad outcomes don't really exist and get rid of the preventative measures. Example, energy independence from Russia and shutting down nuclear reactors. Another example, people think there's no point in taking vaccines.