> What might be interesting is to have a tool that processes full JSON data and creates a b-tree index on specified keys. Then you could run searches against the index that return byte offsets you can use for actual random access on the original JSON.

I did build that once. But keeping track of the index is a pain. Sometimes I was able to generate the index on-demand and cache it in some ephemeral storage, but overall it didn't work out so well.

This system with RX will work better because I get the indexes built-in to the data file and can always convert it back to JSON if needed.