jsonista VS reitit

Reading and writing JSON from Clojure is very easy. Probably the easiest library to use would be clojure.data.json, though it's not the most performant. If you need better performance, jsonista is probably what you need.

I hope they accept my PR

https://github.com/metosin/jsonista for JSON (it's faster and easier to use than cheshire)

I would build the CLJS for your game logic. Then I would build the backend server separately with API endpoints your front end to talk to. https://github.com/metosin/reitit is a pretty good option.

A significant feature of reitit is that routes are composed of simple vectors and maps. That means you can pre-process that data structure however you want before building the router.

You might look at the examples on the Reitit page. Reitit seems to be the emerging library for routing, and it does get you most of the way there, no matter which direction you are looking to go..

for runtime validation & coercion, you can use the pedestal-utilities from reitit which support all of spec, schema and malli. For dev-time var instrumentation (static & dynamic), there are several ways to add those to existing or 3rd party codebases.