Android In-App Subscription Implementation

I am dealing with In-app purchase stuff in Android.

Learned about In-App purchase for different types: Consumable, Non-Consumable and Subscription.

For the Subscription type I come to know that :

If your app stores subscription state on a secure backend server, your app should listen for state changes using Real-time developer notifications to ensure the state is kept in-sync. A SubscriptionNotification is sent for events affecting subscription states such as renewals and cancellations. You need to call the developer API after receiving Real-time developer notifications to get a complete status and update your own backend state. These notifications tell you only that the subscription state changed. They do not give you complete information about the overall subscription status.

Here, secure backend server come in to picture. From the above text content, we know what's the need for it.

But Can We implement Subscription functionality without the use of Back end server?

Can I track the purchased subscription details?

Thanks.