diff --git a/common/src/app/common/transit.cljc b/common/src/app/common/transit.cljc
index dc3e37b380..41b503316f 100644
--- a/common/src/app/common/transit.cljc
+++ b/common/src/app/common/transit.cljc
@@ -99,6 +99,17 @@
 
 ;; --- HANDLERS
 
+#?(:cljs
+   (defn- keyword-reader
+     "Return a reader that gives the same keyword instance for each name."
+     []
+     (let [cache (js/Map.)]
+       (fn [value]
+         (or (.get cache value)
+             (let [kw (keyword value)]
+               (.set cache value kw)
+               kw))))))
+
 (add-handlers!
  #?@(:clj
      [{:id "file"
@@ -119,6 +130,10 @@
     {:id "u"
      :rfn parse-uuid})
 
+ #?(:cljs
+    {:id ":"
+     :rfn (keyword-reader)})
+
  {:id "ordered-map"
   :class #?(:clj LinkedMap :cljs lkm/LinkedMap)
   :wfn vec
diff --git a/common/src/app/common/types/objects_map.cljc b/common/src/app/common/types/objects_map.cljc
index 77289a2b1e..1b4e17ce4c 100644
--- a/common/src/app/common/types/objects_map.cljc
+++ b/common/src/app/common/types/objects_map.cljc
@@ -206,7 +206,7 @@
 
      c/IWithMeta
      (-with-meta [this new-meta]
-       (if (identical? new-meta meta)
+       (if (identical? new-meta metadata)
          this
          (ObjectsMap. new-meta
                       cache
diff --git a/common/src/app/common/types/shape_tree.cljc b/common/src/app/common/types/shape_tree.cljc
index 0080aae00d..05cb0fc40f 100644
--- a/common/src/app/common/types/shape_tree.cljc
+++ b/common/src/app/common/types/shape_tree.cljc
@@ -368,11 +368,17 @@
 
 (defn start-page-index
   [objects]
-  (with-meta objects {::index-frames (get-frames (with-meta objects nil))}))
+  (with-meta objects {::index-frames (into [] (get-frames objects {:ignore-index? true}))}))
 
 (defn update-page-index
+  "Lazy, so pages that are not open are not decoded. The index reads
+  from the returned objects, so decoded shapes are shared with them."
   [objects]
-  (with-meta objects {::index-frames (get-frames (with-meta objects nil))}))
+  (let [self    (volatile! nil)
+        objects (with-meta objects
+                  {::index-frames (lazy-seq (get-frames @self {:ignore-index? true}))})]
+    (vreset! self objects)
+    objects))
 
 (defn update-object-indices
   [file page-id]
diff --git a/frontend/src/app/render_wasm/shape.cljs b/frontend/src/app/render_wasm/shape.cljs
index d94bd8d070..1d2980d6c9 100644
--- a/frontend/src/app/render_wasm/shape.cljs
+++ b/frontend/src/app/render_wasm/shape.cljs
@@ -79,6 +79,16 @@
   (-count [_]
     (+ 1 (count delegate)))
 
+  c/IKVReduce
+  (-kv-reduce [_ f init]
+    (let [acc (f init :id id)]
+      (if (reduced? acc)
+        @acc
+        (let [acc (f acc :type type)]
+          (if (reduced? acc)
+            @acc
+            (reduce-kv f acc delegate))))))
+
   c/ILookup
   (-lookup [coll k]
     (-lookup coll k nil))
@@ -354,6 +364,18 @@
     (let [id (:id self)]
       (.set changes id (conj* (.get changes id) k)))))
 
+(defn- assoc-delegate
+  "Keeps an array map delegate as an array map when adding a new key."
+  [delegate k v]
+  (if (and (instance? PersistentArrayMap delegate)
+           (not (contains? delegate k)))
+    (PersistentArrayMap. (meta delegate)
+                         (inc (count delegate))
+                         (doto (aclone (.-arr ^PersistentArrayMap delegate))
+                           (.push k v))
+                         nil)
+    (assoc delegate k v)))
+
 (defn- impl-assoc
   [self k v]
   (track-change! self k)
@@ -369,7 +391,7 @@
                  (.-delegate ^ShapeProxy self))
 
     (let [delegate  (.-delegate ^ShapeProxy self)
-          delegate' (assoc delegate k v)]
+          delegate' (assoc-delegate delegate k v)]
       (if (identical? delegate' delegate)
         self
         (ShapeProxy. (.-id ^ShapeProxy self)
@@ -418,18 +440,19 @@
                    (next es))
             (throw (js/Error. "conj on a map takes map entries or seqables of map entries"))))))))
 
-(def ^:private xf:without-id-and-type
-  (remove (fn [kvpair]
-            (let [k (key kvpair)]
-              (or (= k :id)
-                  (= k :type))))))
-
 (defn create-shape
-  "Instantiate a shape from a map"
+  "Instantiate a shape from a map. The delegate is an array map because
+  it takes far less memory than a hash map for shape-sized maps."
   [attrs]
-  (ShapeProxy. (:id attrs)
-               (:type attrs)
-               (into {} xf:without-id-and-type attrs)))
+  (let [arr (reduce-kv (fn [arr k v]
+                         (when-not (or (= k :id) (= k :type))
+                           (.push arr k v))
+                         arr)
+                       #js []
+                       attrs)]
+    (ShapeProxy. (:id attrs)
+                 (:type attrs)
+                 (PersistentArrayMap. nil (/ (alength arr) 2) arr nil))))
 
 (t/add-handlers!
  ;; We only add a write handler, read handler uses the dynamic dispatch