Backend Application Flutter

Hello to all,
My goal is to create an application on Flutter. My application will integrate a map where users will be visible live on the map (even when they move). I would like to know which database to use?
I am comfortable with SQL but is it possible to integrate in a table the live position of the users?
Should I use a cloud database like FireBase?
And finally, which DBMS will be the cheapest for an application like mine?

Thanks a lot!

@marco_Milioni Yep its possible but will require a lot of logocal work

You have to use flutter Flutter background geolocation

Get user location and save it in your table
Then on change you have to constantly uodate your tables

And in app u can use geo decoding encodings to show users location
And from that parameters you can also show location on map

Just use this basic idea and implement it to solve your issue
Hit like button if it helps.
Happy fluttetingšŸ˜Ž