Author here!

Sorry that some of the stuff went over your head! I wanted to include longer descriptions of the tech I was using but the post was already suuuper long and I felt like I couldn't add more.

Very happy to answer any questions that you've got here!

I'm not sure how you'd simplify the architecture in a major way to be honest. There are certainly services you could use for stuff like this, but I think there you're offloading the complexity to someone else? Ultimately you need:

    * A database that tracks which boxes are checked (that's Redis)
    * A choice about how to put your data in your database (I chose to just store 1 million bits for simplicity)
    * A way to tell your clients what the current state is (I chose to send them all 1 million bits - it's nice that this is not that much data)
    * A way for clients to tell you when they check a box + update your state (that's Flask + the websocket)
    * A way to tell your clients when a box is checked/unchecked (that's also Flask + websockets. I chose to send both updates about individual boxes and also updates about all 1 million boxes)
    * A way to avoid rendering 1 million dom elements all the time (react-window)

The other stuff (nginx for static content + a reverse proxy) is mostly just to make things easier to scale; you could implement this solution without those details and the site would work fine, it just wouldn't be able to handle the same load.