Meta_query with relation ‘OR’ killing server CPU

Afaik, there’s no relation key for meta_query. Use compare instead and maybe also specify a type to speed things up with skipping types that are out of scope.

EDIT

$args = array(
    'post_type' => 'product',
    'meta_query' => array(
            // Used to set two meta keys IN RELATION TO EACH OTHER
        'relation' => 'OR',
        array(
            'key' => 'color',
            'value' => 'blue',
                    // Used to FILTER OUT/IN/LIKE THE VALUE NAME
            'compare' => 'NOT LIKE'
        ),
        array(
            'key' => 'price',
            'value' => array( 20, 100 ),
            'type' => 'numeric',
            'compare' => 'BETWEEN'
        )
    )
  );
 $query = new WP_Query( $args );