def parse_response(response):
    """
    :param response: output of boto3 rds client describe_db_instances
    :return: an array, each element is an 3-element array with DBInstanceIdentifier, Engine, and Endpoint Address
    Example:
        [
            ['devdb-ldn-test1', 'mysql', 'devdb-ldn-test.cjjimtutptto.eu-west-2.rds.amazonaws.com'],
            ['devdb-ldn-test2', 'postgres', 'devdb-ldn-test.cjjimtutptto.eu-west-2.rds.amazonaws.com'],
            ...
        ]
    """
    res = []
    # json output parse
    for db in response['DBInstances']:
        res.append([db['DBInstanceIdentifier'], db['Engine'], db['Endpoint']['Address']])
    return res