This is really neat! I've been working on an open-source version of the Firebase Realtime Database as well that might be of interest[1]. Also written in Rust! Might be a good basis for building out the Realtime Database part of Firenook if you have any interest in supporting that as well.
Thanks and Lark looks really good and interesting!! Will definitely look into it as I do have plans to integrate Realtime Database into Firenook too :)