Add QuickSync to receive your notifications immediately. This uses Firebase Messaging and it dependents on Google Play Services. Make sure you already have integrated Plot using the Android integration guide.
Step 1: Add Firebase Messaging Dependency

Add a dependency on Firebase in your app-level gradle file. The download page shows with what version it has been tested. It is possible it won’t work with newer major versions of Google Play Services.

dependencies {
  //ensure the version of the Firebase libraries are the same as of your Google Play Services dependency
  compile 'com.google.firebase:firebase-core:' + googlePlayVersion
  compile 'com.google.firebase:firebase-messaging:' + googlePlayVersion
}
Step 2: Add Services

Add a service registration to your manifest as shown in the snippet if you don’t have Firebase Messaging integrated yet.

<service
		android:name="com.plotprojects.retail.android.QuickSyncFirebaseMessagingService">
		<intent-filter>
				<action android:name="com.google.firebase.MESSAGING_EVENT" />
		</intent-filter>
</service>

<service
		android:name="com.plotprojects.retail.android.QuickSyncFirebaseInstanceIdService">
		<intent-filter>
				<action android:name="com.google.firebase.INSTANCE_ID_EVENT" />
		</intent-filter>
</service>

When you have your own Firebase Messaging services inside your app, you can forward calls from these services to our library. The QuickSyncFirebaseInstanceIdService has the static method handleTokenRefresh(Context) for tokenRefresh events and the QuickSyncFirebaseMessagingService has the static method handleMessageReceived(Context, RemoteMessage) for messageReceived events.

Step 3: Setup a Firebase Project

Follow the steps at the Firebase Console to setup your project and make sure you enable cloud messaging for your project.

Step 4: Add Config File

To obtain the google-services.json config file, add your Android app to Firebase by clicking on the "Add Firebase to your Android app" and following the instructions.

 In case your Firebase project already has the Android app, go to the General tab in the Project Settings page and retrieve the config file, as shown in the image below.

Once the google-services.json config is downloaded, add it into your project’s module folder, typically app/.

Step 6: Almost done!

After performing the steps above, in order to get the server key, click the settings button, highlighted in red, followed by Project Settings.

Then look up the Legacy server key found in the Cloud Messaging tab of the Settings page, as presented below.

Add that code to the dashboard in the Developer Tools page.

You are now ready to receive your first notification through QuickSync! For more details, look at the extensive documentation.