database.clj

(ns facebook-example.database
  (:gen-class)
  (:require [clojure.java.io :as io]
            [clojure.data.json :as json]))

(defn load-db []
  (if-let [data (slurp (io/file (io/resource "database.json")))]
    (try (json/read-str data :key-fn keyword)
      (catch Exception e {}))))

(defn write-db [data]
  (with-open [out-file (io/writer "./resources/database.json" :encoding "UTF-8")]
    (.write out-file (json/write-str data)))
  data)

(defn read [key]
  ((keyword key) (load-db))

(defn save [key value]
  (as-> (load-db) data
        (assoc data (keyword key) value)
        (write-db data)))

(defn save-in [keys value]
  (as-> (load-db) data
        (assoc-in data (map keyword keys) value)
        (write-db data)))

Setup:
create an empty file "database.json" in your resources directory
add [facebook-example.database :as db] to your :require statement at the beginning of your bot.clj

Usage:
(db/read sender-id)
(db/save sender-id {"state" "new User"})
(db/save-in [sender-id "state"] "old user")