How to send notification when there is a data change in firebase in Unity?

I have been googling this for a while but I couldn’t get any closer. I’m developing a 2d mobile game in unity and I use Firebase database. What I want to do is a simple friend request system. Assume that there are users A and B. Also, there is a Users node in Firebase realtime database. When user A adds user B as a friend, id of user A is being written in FriendRequests node of User B. Then there should be a notification sent to User B even if the game is not running.

In short, I want to send notification when there is a data change in Firebase real time database in Unity even if the app is closed. How can I achieve that? Thank you in advance for any idea.

alt text

hlw man @serkantarakci did you get any answer for the problem you mentioned above actually i’m trying to achieve something similar to that for my game it would a great help if you will tell me something you did for that thing.