Ugh, is it that time again?

You can't just magically disappear the complexity that is inherent to building actual applications. Synchronizing data based on unique IDs isn't special. At best this is an interesting prototyping tool and at worst this is a huge red flag for your understanding of actual web development.

Of course there is no source code, but we get to bear witness to the great development habits of this author: 105 changed files in his repo.

Pony up some source code and actual details and then we can talk. Until then, as far as I'm concerned, you just demonstrated ready-made components that are talking to firebase or whatever.