Can you talk a little more about your thoughts on one big atom? I've been looking at Redux and they also seem to follow this approach. The re-frame readme quotes the Elm Architecture as justification, but that same document goes on to describe nesting https://gist.github.com/evancz/2b2ba366cae1887fe621#nesting.
I come from a Haskell perspective and having one big blob of state sounds to me like it makes your type signatures less informative and increases the scope for error.
First, in Reagent/FRP, I was updating a view based on the value of an atom. This meant I had different default values in different atoms. The big atom let me unify where I stored values, and reuse values, without a performance hit. Second, the big atom made storing application state trivial: you can just throw the map/record in Redis or something.
However, the big atom is just a big map, and keys can be paired with any value, so it is not enforcing types. From a Haskell perspective (where I understand the program almost falls out of the types you define!), this probably does increase the scope for error.
This can be mitigated with Schema (which I never used effectively), logging changes to the console, and being able to see your default map easily (like, there's a map in one file which I load upfront, so I can see what values are there).
I'd welcome hearing from anyone with a more advanced or precise use of re-frame state.
I come from a Haskell perspective and having one big blob of state sounds to me like it makes your type signatures less informative and increases the scope for error.