Eli5: what happens on the server when one selects to watch a movie on Netflix and how the architecture allows 500k other people to watch the same movie almost concurrently?
In: Technology
Video can be broken down into little bite sized chunks of independent files. So an hour long video is actually made up of maybe 360 chunks of 10 second video files. But your browser/TV is loading a few of these video files at a time so that you have some buffer in case the network has a blip.
A CDN, like other people have said, will “cache” or save a local copy, of some of those chunks. When you go to watch a video, through the magic of the internet, you will be directed to a server near you which also likely has some of these video chunks saved locally (if it’s a popular video). So not only do they not have to load it from the “source of truth”, but the data is close to you.
Depending on how many people are watching the video in your area you can imagine that many servers store these pieces of the video (because the servers have only so much ability to serve viewers). But the viewers are probably spread out across the country or world and one server can serve a lot of different viewers.
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