Notifications

When YouTube was first designed, you can subscribe to our channel and get notifications by default. Notifications are nice because I can get it on my phone. And then I can immediately go and visit the page, right? And get the new video. So that's another example. The final example is I'm not 100% sure about I'm 99.5 sure YouTube. You know why? My guess is that YouTube at a certain point realized that it just the back end couldn't scale enough to notify billions of users by default. Right.