Select only post id and meta value with WP_Query

I'm developing a simple rank plugin, which allows visitors to like the posts and also shows the total like scores for each tag in the plugin's admin page. I need both post IDs (in order to reach the tag data of them) and like values.

This is my query at the moment:

$args = array(
    'meta_key' = '_Like',
    'orderby' = 'meta_value',
);

$query = new WP_Query($args);

But this query returns the complete post object, it's not efficient for the memory. I only need _Like value and the post_id. Is there a better query for this ?