I'm developing this ordering Android app and thought about this problem. Creating an order or fetching user data from the backend is not that important- in case of error, Snackbar, Toast, etc. could be shown to inform user about failed backend call.
But what about Canceling the order? How do I make sure, that no matter what, the POST request to cancel the order, will be sent to the backend?
Thanks in advance :)

Edit: I'm using Firebase Firestore, and I just need to update one value. But I want to make sure, that no matter what (user turns off the internet, kills the app, etc) Firestore will be updated, when internet will be available.