diff --git a/.flowconfig b/.flowconfig
index bc83640d..b3deece7 100644
--- a/.flowconfig
+++ b/.flowconfig
@@ -16,8 +16,7 @@ suppress_comment=\\(.\\|\n\\)*\\$FlowIssue\\((\\(<VERSION>\\)? *\\(site=[a-z,_]*
 suppress_comment=\\(.\\|\n\\)*\\$FlowFixedInNextDeploy
 suppress_comment=\\(.\\|\n\\)*\\$FlowExpectedError
 
-unsafe.enable_getters_and_setters=true
 munge_underscores=true
 
 [version]
-^0.60.0
+^0.66.0
diff --git a/package.json b/package.json
index f79590c8..971c3995 100644
--- a/package.json
+++ b/package.json
@@ -26,7 +26,7 @@
     "eslint-plugin-prettier": "2.6.0",
     "eslint-plugin-react": "7.6.1",
     "eslint-plugin-relay": "0.0.21",
-    "flow-bin": "^0.60.1",
+    "flow-bin": "^0.66.0",
     "glob": "^7.1.1",
     "istanbul-api": "^1.1.0",
     "istanbul-lib-coverage": "^1.0.0",
diff --git a/packages/metro-cache/src/PersistedMapStore.js b/packages/metro-cache/src/PersistedMapStore.js
new file mode 100644
index 00000000..4c44dcd2
--- /dev/null
+++ b/packages/metro-cache/src/PersistedMapStore.js
@@ -0,0 +1,75 @@
+/**
+ * Copyright (c) 2018-present, Facebook, Inc.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ *
+ * @format
+ * @flow
+ */
+
+'use strict';
+
+const fs = require('fs');
+const serializer = require('jest-serializer');
+
+export type Options = {|
+  path: string,
+  writeDelay: ?number,
+|};
+
+class PersistedMapStore {
+  _map: ?Map<string, mixed>;
+  _path: string;
+  _store: () => void;
+  _timeout: ?TimeoutID;
+  _writeDelay: number;
+
+  constructor(options: Options) {
+    this._path = options.path;
+    this._writeDelay = options.writeDelay || 5000;
+
+    this._store = this._store.bind(this);
+    this._timeout = null;
+    this._map = null;
+  }
+
+  get(key: Buffer): mixed {
+    this._getMap();
+
+    if (this._map) {
+      return this._map.get(key.toString('hex'));
+    }
+
+    return null;
+  }
+
+  set(key: Buffer, value: mixed) {
+    this._getMap();
+
+    if (this._map) {
+      this._map.set(key.toString('hex'), value);
+    }
+
+    if (!this._timeout) {
+      this._timeout = setTimeout(this._store, this._writeDelay);
+    }
+  }
+
+  _getMap() {
+    if (!this._map) {
+      if (fs.existsSync(this._path)) {
+        this._map = serializer.readFileSync(this._path);
+      } else {
+        this._map = new Map();
+      }
+    }
+  }
+
+  _store() {
+    serializer.writeFileSync(this._path, this._map);
+    this._timeout = null;
+  }
+}
+
+module.exports = PersistedMapStore;
diff --git a/packages/metro-cache/src/__tests__/PersistedMapStore-test.js b/packages/metro-cache/src/__tests__/PersistedMapStore-test.js
new file mode 100644
index 00000000..bf9e5597
--- /dev/null
+++ b/packages/metro-cache/src/__tests__/PersistedMapStore-test.js
@@ -0,0 +1,121 @@
+/**
+ * Copyright (c) 2018-present, Facebook, Inc.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ *
+ * @emails oncall+javascript_foundation
+ * @format
+ */
+
+'use strict';
+
+describe('PersistedMapStore', () => {
+  const key1 = Buffer.from('foo');
+  const key2 = Buffer.from('bar');
+  let now;
+  let serializer;
+  let fs;
+  let PersistedMapStore;
+
+  function advance(time) {
+    now += time;
+    jest.advanceTimersByTime(time);
+  }
+
+  Date.now = () => now;
+
+  beforeEach(() => {
+    jest
+      .resetModules()
+      .resetAllMocks()
+      .useFakeTimers();
+
+    jest.mock('fs', () => ({
+      existsSync: jest.fn(),
+    }));
+
+    jest.mock('jest-serializer', () => ({
+      readFileSync: jest.fn(),
+      writeFileSync: jest.fn(),
+    }));
+
+    fs = require('fs');
+    serializer = require('jest-serializer');
+    PersistedMapStore = require('../PersistedMapStore');
+
+    now = 0;
+  });
+
+  it('ensures that the persisted map file is checked first', () => {
+    const store = new PersistedMapStore({path: '/foo'});
+
+    fs.existsSync.mockReturnValue(false);
+    store.get(key1);
+
+    expect(fs.existsSync).toHaveBeenCalledTimes(1);
+    expect(serializer.readFileSync).not.toBeCalled();
+  });
+
+  it('loads the file when it exists', () => {
+    const store = new PersistedMapStore({path: '/foo'});
+
+    fs.existsSync.mockReturnValue(true);
+    serializer.readFileSync.mockReturnValue(new Map());
+    store.get(key1);
+
+    expect(fs.existsSync).toHaveBeenCalledTimes(1);
+    expect(serializer.readFileSync).toHaveBeenCalledTimes(1);
+    expect(serializer.readFileSync.mock.calls[0]).toEqual(['/foo']);
+  });
+
+  it('throws if the file is invalid', () => {
+    const store = new PersistedMapStore({path: '/foo'});
+
+    fs.existsSync.mockReturnValue(true);
+    serializer.readFileSync.mockImplementation(() => {
+      throw new Error();
+    });
+    expect(() => store.get(key1)).toThrow();
+  });
+
+  it('deserializes and serializes correctly from/to disk', () => {
+    let file;
+
+    fs.existsSync.mockReturnValue(false);
+    serializer.readFileSync.mockImplementation(() => file);
+    serializer.writeFileSync.mockImplementation((_, data) => (file = data));
+
+    const store1 = new PersistedMapStore({path: '/foo'});
+
+    store1.set(key1, 'value1');
+    store1.set(key2, 123456);
+
+    // Force throttle to kick in and perform the file storage.
+    advance(7500);
+    fs.existsSync.mockReturnValue(true);
+
+    const store2 = new PersistedMapStore({path: '/foo'});
+
+    expect(store2.get(key1)).toBe('value1');
+    expect(store2.get(key2)).toBe(123456);
+  });
+
+  it('ensures that the throttling is working correctly', () => {
+    const store1 = new PersistedMapStore({
+      path: '/foo',
+      writeDelay: 1234,
+    });
+
+    // Triggers the write, multiple times (only one write should happen).
+    store1.set(key1, 'foo');
+    store1.set(key1, 'bar');
+    store1.set(key1, 'baz');
+
+    advance(1233);
+    expect(serializer.writeFileSync).toHaveBeenCalledTimes(0);
+
+    advance(1);
+    expect(serializer.writeFileSync).toHaveBeenCalledTimes(1);
+  });
+});
diff --git a/yarn.lock b/yarn.lock
index 42a4e367..9f9197d4 100644
--- a/yarn.lock
+++ b/yarn.lock
@@ -1436,7 +1436,7 @@ babylon@7.0.0-beta.36:
   version "7.0.0-beta.36"
   resolved "https://registry.yarnpkg.com/babylon/-/babylon-7.0.0-beta.36.tgz#3a3683ba6a9a1e02b0aa507c8e63435e39305b9e"
 
-babylon@^7.0.0-beta, babylon@7.0.0-beta.38:
+babylon@7.0.0-beta.38, babylon@^7.0.0-beta:
   version "7.0.0-beta.38"
   resolved "https://registry.yarnpkg.com/babylon/-/babylon-7.0.0-beta.38.tgz#9b3a33e571a47464a2d20cb9dd5a570f00e3f996"
 
@@ -2527,9 +2527,9 @@ flat-cache@^1.2.1:
     graceful-fs "^4.1.2"
     write "^0.2.1"
 
-flow-bin@^0.60.1:
-  version "0.60.1"
-  resolved "https://registry.yarnpkg.com/flow-bin/-/flow-bin-0.60.1.tgz#0f4fa7b49be2a916f18cd946fc4a51e32ffe4b48"
+flow-bin@^0.66.0:
+  version "0.66.0"
+  resolved "https://registry.yarnpkg.com/flow-bin/-/flow-bin-0.66.0.tgz#a96dde7015dc3343fd552a7b4963c02be705ca26"
 
 for-in@^1.0.1:
   version "1.0.2"