You'll need compojure-api 1.2.0-alpha7. There's some info in https://github.com/metosin/compojure-api/wiki/Async and examples of async handlers in https://github.com/metosin/compojure-api/blob/master/examples/async/src/example/handler.clj

(Sorry but I have to go now, so I don't have to time to elaborate.)