I've just been dogfooding whatever I can to build it out.

Webpages, zettelkasten, todo, workout, diet tracker. It's a web framework! Creating an endpoint is just like making a function in emacs.

Since lisp is homoiconic the AST is just raw JSON. I save the AST in JSON stores in Postgres. But you can clone the AST down and then eval against a local copy of the REPl. So you get local eval for free.

Of course you have to rebuild git to manage a branching REPL in this way.