Example: "How to use multiple databases django"

gistfile1.txt

You can easy do this by appearing custom attribute to model:

class A(models.Model):
    _DATABASE = "X"

class B(models.Model):
    _DATABASE = "X"
...

Then you need to add router. Next one will select database by _DATABASE field, and models without _DATABASE attribute will select default database, also relationships will be allowed only for default database:

class CustomRouter(object):


    def db_for_read(self, model, **hints):
        database = getattr(model, "_DATABASE", None)
        if database:
            return database
        else:
            return "default"

    def db_for_write(self, model, **hints):
        database = getattr(model, "_DATABASE", None)
        if database:
            return database
        else:
            return "default"

    def allow_relation(self, obj1, obj2, **hints):
        """
        Relations between objects are allowed if both objects are
        in the master/slave pool.
        """
        db_list = ('default')
        if obj1._state.db in db_list and obj2._state.db in db_list:
            return True
        return None

    def allow_migrate(self, db, model):
        """
        All non-auth models end up in this pool.
        """
        return True  

And the last step is specifing your router in settings.py:

DATABASE_ROUTERS = ['path.to.class.CustomRouter']