def processed_events(object_type: str, subscriber: str) -> str:
    """Return the db key used to store processed events.

    This is the key where processed events for the specified subscriber and
    object type are stored.

    Args:
        object_type (str): Type of object
        subscriber (str): Subscriber name

    Returns:
        str, db key where processed events are stored.

    """
    return 'events:{}:{}:processed'.format(object_type, subscriber)