Index: oak-core/src/main/java/org/apache/jackrabbit/oak/plugins/mongomk/Commit.java
===================================================================
--- oak-core/src/main/java/org/apache/jackrabbit/oak/plugins/mongomk/Commit.java	(revision 1558009)
+++ oak-core/src/main/java/org/apache/jackrabbit/oak/plugins/mongomk/Commit.java	(working copy)
@@ -452,6 +452,10 @@
         addOrRemove.addAll(addedNodes);
         addOrRemove.addAll(removedNodes);
         for (String p : addOrRemove) {
+            if (PathUtils.denotesRoot(p)) {
+                // special case: root node was added
+                continue;
+            }
             String parent = PathUtils.getParentPath(p);
             ArrayList<String> list = nodesWithChangedChildren.get(parent);
             if (list == null) {
@@ -478,7 +482,7 @@
             boolean pendingLastRev = op == null
                     || !NodeDocument.hasLastRev(op, revision.getClusterId());
             boolean isDelete = op != null && op.isDelete();
-            nodeStore.applyChanges(revision, path, isNew, isDelete, pendingLastRev, isBranchCommit, added, removed);
+            nodeStore.applyChanges(revision, baseRevision, path, isNew, isDelete, pendingLastRev, isBranchCommit, added, removed);
         }
     }
 
Index: oak-core/src/main/java/org/apache/jackrabbit/oak/plugins/mongomk/MongoNodeStore.java
===================================================================
--- oak-core/src/main/java/org/apache/jackrabbit/oak/plugins/mongomk/MongoNodeStore.java	(revision 1558009)
+++ oak-core/src/main/java/org/apache/jackrabbit/oak/plugins/mongomk/MongoNodeStore.java	(working copy)
@@ -677,6 +677,15 @@
 
     @CheckForNull
     Node readNode(String path, Revision readRevision) {
+        if (!PathUtils.denotesRoot(path)) {
+            // check children cache first
+            String parentKey = PathUtils.getParentPath(path) +
+                    "@" + readRevision;
+            Node.Children c = nodeChildrenCache.getIfPresent(parentKey);
+            if (c != null && !c.hasMore && !c.children.contains(path)) {
+                return null;
+            }
+        }
         String id = Utils.getIdFromPath(path);
         Revision lastRevision = getPendingModifications().get(path);
         NodeDocument doc = store.find(Collection.NODES, id);
@@ -689,7 +698,8 @@
     /**
      * Apply the changes of a node to the cache.
      *
-     * @param rev the revision
+     * @param rev the commit revision.
+     * @param base the base revision of the commit.
      * @param path the path
      * @param isNew whether this is a new node
      * @param isDelete whether the node is deleted
@@ -699,7 +709,7 @@
      * @param removed the list of removed child nodes
      *
      */
-    public void applyChanges(Revision rev, String path,
+    public void applyChanges(Revision rev, Revision base, String path,
                              boolean isNew, boolean isDelete, boolean pendingLastRev,
                              boolean isBranchCommit, ArrayList<String> added,
                              ArrayList<String> removed) {
@@ -723,20 +733,38 @@
                 }
             }
         }
-        String key = path + "@" + rev;
+        String key = path + "@" + (isBranchCommit ? rev.asBranchRevision() : rev);
         Node.Children c = nodeChildrenCache.getIfPresent(key);
         if (isNew || (!isDelete && c != null)) {
+            // we can put the result of the operations into the
+            // cache if this is a new node. there can be no other
+            // commit adding children to this node concurrently
             Node.Children c2 = new Node.Children();
             TreeSet<String> set = new TreeSet<String>();
             if (c != null) {
                 set.addAll(c.children);
             }
             set.removeAll(removed);
-            for (String name : added) {
-                set.add(Utils.unshareString(name));
+            for (String p : added) {
+                set.add(Utils.unshareString(p));
             }
             c2.children.addAll(set);
             nodeChildrenCache.put(key, c2);
+        } else if (isBranchCommit) {
+            // branch commits are isolated, hence we can calculate
+            // the new cache entry from the entry for the base revision
+            // (if available and complete).
+            c = nodeChildrenCache.getIfPresent(path + "@" + base);
+            if (c != null && !c.hasMore) {
+                Node.Children c2 = new Node.Children();
+                TreeSet<String> set = new TreeSet<String>(c.children);
+                set.removeAll(removed);
+                for (String p : added) {
+                    set.add(Utils.unshareString(p));
+                }
+                c2.children.addAll(set);
+                nodeChildrenCache.put(key, c2);
+            }
         }
         if (!added.isEmpty()) {
             NodeDocument.Children docChildren = docChildrenCache.getIfPresent(path);
Index: oak-core/src/test/java/org/apache/jackrabbit/oak/plugins/mongomk/SimpleTest.java
===================================================================
--- oak-core/src/test/java/org/apache/jackrabbit/oak/plugins/mongomk/SimpleTest.java	(revision 1558009)
+++ oak-core/src/test/java/org/apache/jackrabbit/oak/plugins/mongomk/SimpleTest.java	(working copy)
@@ -71,16 +71,17 @@
     @Test
     public void addNodeGetNode() {
         MongoMK mk = new MongoMK.Builder().open();
-        Revision rev = Revision.fromString(mk.getHeadRevision());
+        MongoNodeStore ns = mk.getNodeStore();
+        Revision rev = ns.newRevision();
         Node n = new Node("/test", rev);
         n.setProperty("name", "Hello");
         UpdateOp op = n.asOperation(true);
         // mark as commit root
         NodeDocument.setRevision(op, rev, "c");
         DocumentStore s = mk.getDocumentStore();
-        MongoNodeStore ns = mk.getNodeStore();
         assertTrue(s.create(Collection.NODES, Lists.newArrayList(op)));
         Node n2 = ns.getNode("/test", rev);
+        assertNotNull(n2);
         assertEquals("Hello", n2.getProperty("name"));
         mk.dispose();
     }