diff --git a/packages/core/database/collection.js b/packages/core/database/collection.js
new file mode 100644
index 000000000..a0fbe919e
--- /dev/null
+++ b/packages/core/database/collection.js
@@ -0,0 +1,44 @@
+import Indexer from "./indexer";
+
+export default class Collection extends Indexer {
+  constructor(context, type) {
+    super(context, type);
+    this.collection = new Map();
+  }
+
+  async initCollection() {
+    await this.initIndexer();
+  }
+
+  async addItem(item) {
+    this.collection.set(item.id, item);
+    await this.write(item.id, item);
+    await this.index(item.id);
+  }
+
+  async removeItem(id) {
+    if (this.collection.delete(id)) {
+      this.remove(id);
+      await this.deindex(id);
+    }
+  }
+
+  async getItem(id) {
+    if (this.collection.has(id)) {
+      return this.collection.get(id);
+    } else {
+      return await this.read(id);
+    }
+  }
+
+  async getAllItems() {
+    let items = [];
+    for (let id of await this.getIndices()) {
+      let item = await this.getItem(id);
+      if (item) {
+        items[items.length] = item;
+      }
+    }
+    return items;
+  }
+}
diff --git a/packages/core/database/indexer.js b/packages/core/database/indexer.js
new file mode 100644
index 000000000..e66f2391a
--- /dev/null
+++ b/packages/core/database/indexer.js
@@ -0,0 +1,33 @@
+import Storage from "./storage";
+
+export default class Indexer extends Storage {
+  constructor(context, type) {
+    super(context);
+    this.type = type;
+    this.indices = [];
+  }
+
+  async initIndexer() {
+    this.indices = (await this.read(this.type)) || [];
+  }
+
+  async index(key) {
+    if (this.indices.length <= 0) {
+      this.indices = (await this.read(this.type)) || [];
+    }
+    this.indices[this.indices.length] = key;
+    await this.write(this.type, this.indices);
+  }
+
+  async getIndices() {
+    if (this.indices.length <= 0) {
+      this.indices = (await this.read(this.type)) || [];
+    }
+    return this.indices;
+  }
+
+  async deindex(key) {
+    this.indices.splice(this.indices.indexOf(key), 1);
+    await this.write(this.type, this.indices);
+  }
+}
diff --git a/packages/core/database/storage.js b/packages/core/database/storage.js
new file mode 100644
index 000000000..ce107ca16
--- /dev/null
+++ b/packages/core/database/storage.js
@@ -0,0 +1,26 @@
+import Convert from "../utils/convert";
+
+export default class Storage {
+  constructor(context) {
+    this.storage = context;
+  }
+  async write(key, data) {
+    await this.storage.write(key, Convert.toString(data));
+  }
+  async read(key) {
+    let data = await this.storage.read(key);
+    return Convert.fromString(data);
+  }
+  clear() {
+    this.storage.clear();
+  }
+  remove(key) {
+    this.storage.remove(key);
+  }
+  encrypt(password, data) {
+    return this.storage.encrypt(password, data);
+  }
+  decrypt(password, cipher) {
+    return this.storage.decrypt(password, cipher);
+  }
+}