Yes its possible
U have to use firebase and Background tasks extension and Notification style extension .
No matter which database are u using
U should have a table/ bucket for notifications
Here u have to save values Iike who posted, who liked etc in your database
And one bucked like data chenged in flutter
Now whenever something changes or updated in your database by someone
U have to save value 1 for first time (and them every time it must be incremented by one) in data changed bucket
And in your app there must be a block that checks if data is changed in
If yes then do search in your notifications table!/ bucket of database and search which changes have been made
After getting data by using background taska extension
U can show it by using
notification style extension
Its an overview u have to work on your logic for making it effective
But its not a hard task