Python Postgres JSON

Currently as written I insert the payload as JSON into a single column. I want to break the k/v into columns in the predefined table. The value from MQTT is always byte object. ie...

b'{"name":"John","age":30,"city":"New York"}'

def insertIntoDatabase(message):
    """Inserts the mqtt data into the database"""

    with connection.cursor() as cursor:
        print("Inserting data...)
        # MQTT message always a byte object
        # message.payload contains message sent in this format 
        b'{"name":"John","age":30,"city":"New York"}'
        # Covert to string ***WORKS***
        test_json = message.payload.decode('utf8')
        # Convert string to dict ***WORKS***
        json_dict = json.loads(test_json)
        print(json_dict)
        # How do I deconstruct the dict into an sql insert???? 
        # Inserts JSON into single column. Need one column per key
        cursor.callproc('InsertIntoMQTTTable', [str(message.topic), 
                        str(message.payload)[2:][:-1], int(message.qos)])
        connection.commit()

SQL Routine - Called via callproc

    create function insertintomqtttable(topic text, message text, 
    qos numeric) returns void
    
    language plpgsql
    as
    $$
        BEGIN
        INSERT INTO mqtt (createdAt, topic, message, qos)
        VALUES (CURRENT_TIMESTAMP, topic, message, qos);
        END;
    $$;

    alter function insertintomqtttable(text, text, numeric) owner to don;

postgres Table Structure -

    CREATE TABLE mqtt (
        id SERIAL PRIMARY KEY,
        createdAt TIMESTAMP NOT NULL,
        topic TEXT NOT NULL,
        message TEXT,
        qos NUMERIC(1) NOT NULL
     );