diff --git a/src/darkleaf/di/core.clj b/src/darkleaf/di/core.clj
index 011bac8c..2ab0e49f 100644
--- a/src/darkleaf/di/core.clj
+++ b/src/darkleaf/di/core.clj
@@ -780,3 +780,53 @@
                ~@body))
            (finally
              (.close resource#)))))))
+
+;; может быть сделать 2 арности в одной функции вместо этих 2х функций?
+
+(defn collect-cache []
+  (let [cache (atom {:started? true})]
+    (fn [registry]
+      (fn [key]
+        (if (= ::cache key)
+          (reify p/Factory
+            (dependencies [_]
+              nil)
+            (build [_ _]
+              cache)
+            (demolish [_ obj]
+              (reset! cache {:started? false})))
+          (let [factory (registry key)]
+            (reify p/Factory
+              (dependencies [_]
+                (p/dependencies factory))
+              (build [_ deps]
+                (let [obj (p/build factory deps)]
+                  (when-not (contains? deps ::cache)
+                    (swap! cache assoc
+                           [:key->deps key] deps
+                           [:key->obj  key] obj))
+                  obj))
+              (demolish [_ obj]
+                (p/demolish factory obj)))))))))
+
+(defn use-cache [cache]
+  (fn [registry]
+    (fn [key]
+      (let [factory     (registry key)
+            cache       @cache
+            cached-deps (cache [:key->deps key])
+            cached-obj  (cache [:key->obj  key])]
+        (when-not (:started? cache)
+          (throw (IllegalStateException. "Invalid cache")))
+        (reify p/Factory
+          (dependencies [_]
+            (p/dependencies factory))
+          (build [_ deps]
+            (if (= cached-deps deps)
+              cached-obj
+              (p/build factory deps)))
+          (demolish [_ obj]
+            ;;todo: add test
+            #_(if (identical? cached-obj obj)
+                nil
+                (p/demolish factory obj))))))))
diff --git a/test/darkleaf/di/cache_test.clj b/test/darkleaf/di/cache_test.clj
new file mode 100644
index 00000000..8d24ed14
--- /dev/null
+++ b/test/darkleaf/di/cache_test.clj
@@ -0,0 +1,109 @@
+(ns darkleaf.di.cache-test
+  (:require
+   [clojure.test :as t]
+   [darkleaf.di.core :as di]))
+
+(set! *warn-on-reflection* true)
+
+
+;; мне надоело логгеры писать
+;; может уже написать реестр, который логирует все действия?
+;; только его нужно передавать извне
+;; (atom [ [`key :started] [`key :stopped] ] )
+(defn a
+  {::di/kind :component}
+  ;; {::di/stop #(swap! (:log %))}
+
+  []
+  [{log ::log}]
+  {:name :a
+   :obj  (Object.)})
+
+(t/deftest a-test
+  (di/with-open [[main cache] (di/start [`a ::di/cache]
+                                        (di/collect-cache))
+                 [secondary]  (di/start [`a]
+                                        (di/use-cache cache))]
+    (t/is (not= nil   main secondary))
+    (t/is (identical? main secondary))))
+
+(defn b
+  {::di/kind :component}
+  [{conf "B_CONF"}]
+  {:name :b
+   :conf conf
+   :obj  (Object.)})
+
+(t/deftest b-test
+  (di/with-open [[main cache] (di/start [`b ::di/cache]
+                                        {"B_CONF" "conf"}
+                                        ;; должен быть последним в цепочке, чтобы закешировать все
+                                        (di/collect-cache))
+                 [secondary]  (di/start [`b]
+                                        (di/use-cache cache))]
+    (t/is (not= nil   main secondary))
+    (t/is (identical? main secondary))))
+
+(t/deftest b-changed-test
+  (di/with-open [[main cache] (di/start [`b ::di/cache]
+                                        {"B_CONF" "conf"}
+                                        (di/collect-cache))
+                 [secondary]  (di/start [`b]
+                                        ;; должен быть первым, чтобы его можно было переопределять
+                                        (di/use-cache cache)
+                                        {"B_CONF" "changed"})]
+    (t/is (not= nil        main secondary))
+    (t/is (not (identical? main secondary)))))
+
+(defn c
+  {::di/kind :component}
+  [{a `a, b `b}]
+  {:name :c
+   :a    a
+   :b    b
+   :obj  (Object.)})
+
+(t/deftest c-test
+  (di/with-open [[main cache] (di/start [`c ::di/cache]
+                                        {"B_CONF" "conf"}
+                                        (di/collect-cache))
+                 [secondary]  (di/start [`c]
+                                        (di/use-cache cache))]
+    (t/is (not= nil   main secondary))
+    (t/is (identical? main secondary))))
+
+(t/deftest c-changed-test
+  (di/with-open [[main cache] (di/start [`c ::di/cache]
+                                        {"B_CONF" "conf"}
+                                        (di/collect-cache))
+                 [secondary]  (di/start [`c]
+                                        (di/use-cache cache)
+                                        {"B_CONF" "changed"})]
+    (t/is (not= nil        main secondary))
+    (t/is (not (identical? main secondary)))
+    (t/is (= :c
+             (:name main)
+             (:name secondary)))
+    (t/is (identical? (:a main)
+                      (:a secondary)))
+    (t/is (not (identical? (:b main)
+                           (:b secondary))))
+    ;; надо ли проверять?
+    (t/is (not (identical? (:obj main)
+                           (:obj secondary))))))
+
+(t/deftest invalid-cache-test
+  (let [[main cache :as system] (di/start [`c ::di/cache]
+                                          {"B_CONF" "conf"}
+                                          (di/collect-cache))
+        _    (di/stop system)]
+    (t/is (thrown? IllegalStateException
+                   (di/start `c
+                             (di/use-cache cache))))))
+
+(t/deftest not-recursive-test
+  (di/with-open [[main cache] (di/start [`c ::di/cache]
+                                        {"B_CONF" "conf"}
+                                        (di/collect-cache))]
+    (t/try-expr "must not be recrusive"
+                (prn-str cache))))
diff --git a/test/darkleaf/di/tutorial/z_memoize_test.clj b/test/darkleaf/di/tutorial/z_memoize_test.clj
new file mode 100644
index 00000000..8d6a15c1
--- /dev/null
+++ b/test/darkleaf/di/tutorial/z_memoize_test.clj
@@ -0,0 +1,53 @@
+(ns darkleaf.di.tutorial.z-memoize-test ;;todo: name
+  (:require
+   [clojure.test :as t]
+   [darkleaf.di.core :as di]))
+
+(defn connection
+  {::di/stop #(reset! % :stopped)}
+  [{url "CONNECTION_URL"}]
+  (atom :started))
+
+(defn migrations
+  "A long running side effect"
+  {::di/kind :component}
+  [{connection `connection}]
+  #_
+  (when (= :stopped @connection)
+    (throw (IllegalStateException. "Connection is not started")))
+  (random-uuid))
+
+(defn root
+  {::di/kind :component}
+  [{migrations `migrations}]
+  {:migrations migrations})
+
+;; todo: check registry placement
+
+(t/deftest ok
+  (let [[cache global-system :as root]
+        (di/start [::di/cache `root]
+                  {"CONNECTION_URL" "1"}
+                  (di/collect-cache))]
+
+    (with-open [local (di/start `root
+                                (di/use-cache cache))]
+      (t/is (identical? global-system @local)))
+
+    (with-open [local (di/start `root
+                                (di/use-cache cache)
+                                {"CONNECTION_URL" "1"})]
+      (t/is (identical? global-system @local)))
+
+    (with-open [local (di/start `root
+                                ;; `use-cache` should be the first registry
+                                (di/use-cache cache)
+                                {"CONNECTION_URL" "2"})]
+      (t/is (not (identical? global-system @local))))
+
+
+    (di/stop root)
+
+    (t/is (thrown? IllegalStateException
+                   (di/start `root
+                             (di/use-cache cache))))))