diff --git a/packages/engine/demo/data-lost-test.js b/packages/engine/demo/data-lost-test.js
index 0920ed94..d8d9605e 100644
--- a/packages/engine/demo/data-lost-test.js
+++ b/packages/engine/demo/data-lost-test.js
@@ -6,37 +6,56 @@ const logger = createLogger('AlwatrStore/Demo', true);
 logger.banner('AlwatrStore/Demo');
 
 const alwatrStore = new AlwatrStore({
-  rootPath: './db'
+  rootPath: './db',
+  defaultChangeDebounce: 250, // for demo
 });
 
-const docId = {
-  name: 'data-lost-test',
-  region: Region.Public,
-}
+const list = [];
+
+for (let i = 0; i < 10; i++) {
+  /**
+   * @type
+   */
+  const docId = {
+    name: 'profile',
+    region: Region.PerUser,
+    ownerId: `u${i}-hash-126789`,
+  };
+
+  if (!alwatrStore.exists(docId)) {
+    alwatrStore.defineStoreFile({
+      ...docId,
+      type: StoreFileType.Collection,
+      extension: StoreFileExtension.Json,
+    });
+  }
 
-if (!alwatrStore.exists(docId)) {
-  alwatrStore.defineStoreFile({
-    ...docId,
-    type: StoreFileType.Collection,
-    extension: StoreFileExtension.Json,
-  });
+  list.push(await alwatrStore.collection(docId));
 }
 
-const collection = await alwatrStore.collection(docId);
+function insertData() {
+  const collection = list[Math.floor(Math.random() * list.length)];
 
-function insertData () {
-  const id = collection.append({
+  let itemId = collection.append({
     name: (Math.random() * 10000).toString(36),
     age: Math.floor(Math.random() * 80) + 10,
   });
 
-  console.log('Inserted', id);
 
-  if (Math.random() < 0.01) {
+  console.log('Collection: %s, itemId:', collection.id, itemId);
+
+  itemId = list[0].append({
+    name: (Math.random() * 10000).toString(36),
+    age: 15,
+  })
+
+  console.log('Collection0, itemId:', itemId);
+
+  if (Math.random() < 0.001) {
     throw new Error('unexpected_random_error');
   }
 
-  setTimeout(insertData, 5);
+  setTimeout(insertData, 2);
 }
 
 insertData();