As I posted above, they own BAMTech, one of the most well respected companies in the streaming infrastructure space.
Building for scale is not hard for good engineers, building for rapid, reliable scale from day one is hard. No one knows how to do it. Building for scale is always about patching holes while you grow slowly.
Even Google doesn’t do big band released like Disney tried to do. They keep things in beta, start off with a limited number of invitations until they work all of the kinks out.
Netflix didn’t become popular overnight. They had time to scale out slowly and on different devices.