from typing import List


def _get_difference_by(fields1: List[str], fields2: List[str]) -> List[str]:
    """Get list with common fields used to decimate and difference given Datasets

    Args:
        fields1: Fields of 1st Dataset
        fields2: Fields of 2nd Dataset
    
    Returns:
        List with common fields to decimate and difference given Datasets
    """
    difference_by = []
    common_fields = set(fields1) & set(fields2)

    for field in ["time", "satellite"]:
        if field in common_fields:
            difference_by.append(field)

    return difference_by