> The app is simple but doing simple things at scale is hard. I wonder if we'll see more downtime and issues now.

So, here's what I've never figured out...

Once your app is built, and you've figured out how to scale it, and everything is autoscaling nicely, and you've reached the critical mass Twitter has...why do you still need all the engineers? Why do you need to keep growing?

At some point, isn't the scaling solved? Once you have a platform that can handle 400M MAUs, what more is there to build?

Does it really take 1,000 engineers to maintain? I'd think automation could take care of most grunt work involved with maintenance.