datoms_example.clj

(defn datoms-for-adding-employee
  [system-user employee-name initial-services-offered]
  [{:db/id             (d/tempid :db.part/user)
    :employee/name     employee-name
    :employee/services initial-services-offered}
   {:db/id           (d/tempid :db.part/tx)
    :command/id      :add-employee
    :command/done-by (:db/id system-user)}])

(let [datoms (datoms-for-adding-employee (:user session)
                                         "Tracey"
                                         #{[:service/name "Eyebrow Waxing"]})]
  (d/transact conn datoms))



(let [datoms (new-booking-datoms start-time end-time employee service client)
      hypothetical-db (d/with db datoms)
      valid (no-overlapping-bookings-for hypothetical-db
                                         employee
                                         client)]
  (when valid
    (d/transact datoms)))