WP_Query with multiple meta_queries joined by AND
$args = array(
'post_type' => 'produkty',
'meta_query' => array(
'relation' => 'AND',
array(
'key' => 'field_name_1',
'value' => '1',
'compare' => '='),
array(
'key' => 'field_name_2',
'value' => '1',
'compare' => '=')
)
);
$query = new WP_Query( $args );