def get_last_aws_update(event_details):
    """
    Takes as input the event_details and returns the last update from AWS (instead of the entire timeline)

    :param event_details: Detailed information about a specific AWS health event.
    :type event_details: dict
    :return: the last update message from AWS
    :rtype: str
    """
    aws_message = event_details['successfulSet'][0]['eventDescription']['latestDescription']
    return aws_message