def mongo2key(mongo_id):
    """Return an (int, string) plate-well key, given its string.

    Parameters
    ----------
    mongo_id : string
        A string representing a plate-well key, separated by a dash.

    Returns
    -------
    tup : (int, string) tuple
        The plate-well representation.

    Examples
    --------
    >>> mongo_id = "2490688-C04"
    >>> mongo2key(mongo_id)
    (2490688, 'C04')
    """
    tup = mongo_id.split('-')
    tup[0] = int(tup[0])
    return tuple(tup)
