def METHOD_NAME(self, start, end):
    """It is used to determine the bucket size using _esUnits
    :param int start: epoch time
    :param int end: epoch time
    :return: S_OK/S_ERROR with tuple of (binUnit, seconds)
    """
    diff = end - start
    error = "Can not determine the bucket size..."
    bucketSeconds = {}
    try:
        # Convert intervals into seconds
        for interval, binUnit in self.__esbucket.items():
            bucketSeconds[_convertToMilliseconds(interval)] = (binUnit, _convertToMilliseconds(binUnit))
        # Determine bin size according to time span
        for interval in sorted(bucketSeconds):
            if diff <= interval:
                return S_OK(bucketSeconds[interval])
    except ValueError as e:
        error += ": " + repr(e)
    return S_ERROR(error)