(defn compile-get-in [path]
  (let [f (reduce
                (fn [acc k]
                    (fn [m] (get (acc m) k)))
                  identity path)]
                (fn [m]
                    (f m))))

(let [m {:a {:b 1}}]
      (time (dotimes [i 100000]
                     (get-in m [:a :b]))))
;; => "Elapsed time: 11.897221 msecs"

 (let [m {:a {:b 1}}
       compiled-get-in-fn (compile-get-in [:a :b])]
     (time (dotimes [i 100000]
                    (compiled-get-in-fn m))))
;; => "Elapsed time: 5.3357 msecs"

;; Significantly more efficient for larger paths and matching maps
 (let [m {:a {:b {:c {:d 1}}}},
       compiled-get-in-fn (compile-get-in [:a :b :c :d])]
     (time (dotimes [i 100000]
                    (compiled-get-in-fn m))))
;; => "Elapsed time: 8.376878 msecs"

(let [m {:a {:b {:c {:d 1}}}}]
     (time (dotimes [i 100000]
                    (get-in m [:a :b :c :d]))))
;; => "Elapsed time: 14.608494 msecs"

;; Benefit seems to get smaller with an increasing path size and no match
;; One option would be to terminate the loop premature when sentinel value has been found

(let [m {:a {:b 1}}]
     (time (dotimes [i 100000]
                    (get-in m [:a :b :c :d]))))
;; => "Elapsed time: 22.612878 msecs"

(let [m {:a {:b 1}},
      compiled-get-in-fn (compile-get-in [:a :b :c :d])]
    (time (dotimes [i 100000]
                   (compiled-get-in-fn m))))
  ;; => "Elapsed time: 18.415237 msecs"


  ;; Adjusted version for no matching paths?

   (defn compile-get-in [path]
     (let [f (reduce
                (fn [acc k]
                    (fn [m] (when-let [m0 (acc m)]
                              (get m0 k))))
                  identity path)]
                (fn [m]
                    (f m))))

(let [m {:a {:b 1}},
      compiled-get-in-fn (compile-get-in [:a :b :c :d])]
    (time (dotimes [i 100000]
                   (compiled-get-in-fn m))))
;; => "Elapsed time: 12.751598 msecs"

;; Matched version is faster?
 (let [m {:a {:b {:c {:d 1}}}},
       compiled-get-in-fn (compile-get-in [:a :b :c :d])]
     (time (dotimes [i 100000]
                    (compiled-get-in-fn m))))
;; => "Elapsed time: 7.738589 msecs"