-sharp models
class User(db.Model):
    __tablename__ = "users"
    id = db.Column(db.BigInteger, primary_key=True)
    name = db.Column(db.VARCHAR(50), nullable=False)
    email = db.Column(db.VARCHAR(200), nullable=False)
    -sharp  NULL
    mobile = db.Column(db.VARCHAR(20), server_default=text("NULL"))

    -sharp 
    password = db.Column(db.VARCHAR, nullable=False)

    -sharp 
    _2fa = db.Column(db.VARCHAR(32), nullable=True)

    -sharp 
    created_at = db.Column(db.TIMESTAMP(False), nullable=False, server_default=text("now()"))

    __table_args__ = (
        Index("idx_users_name", func.lower("name"), unique=True),
        Index("idx_users_email", func.lower("email"), unique=True)
    )

    def __init__(self):
        if not self.created_at:
            self.created_at = now().format()

    def __repr__(self):
        return "<User %s>" % self.name

but there is no duplicate name and email