Crushes server on reciprocal connections on big database table?

I’ve happily used Posts2Posts for several years for a connection between my WordPress install’s main post type and a smaller custom post type —?works great! But recently, I created a new connection where both sides are the main post type. (It’s to connect two different posts that are translated versions of one another —?say, the English and Portuguese versions of the same story.)

function my_translation_connection_types() {
	if ( !function_exists( 'p2p_register_connection_type' ) )
		return;
	p2p_register_connection_type( array( 
		'name' => 'language_to_language',
		'from' => 'post',
		'to' => 'post',
		'reciprocal' => true,
		'title' => 'Translated versions',
		'admin_box' => array(
			'show' => 'any',
			'context' => 'side'
		)
	) );
}
add_action( 'init', 'my_translation_connection_types', 100 );

But when I try to check that connection from a WP template page, it works fine —?but over a period of time, the entire site gets extremely slow, MySQL runs super hot, and eventually everything crashes —?and then repeat. Server logs and P3 Profiler agree that it’s this Posts2Posts call that is doing it; when I comment out the section below in the template file, the crashing stops.

$connected = new WP_Query( array(
  'connected_type' => 'language_to_language',
  'connected_items' => get_queried_object(),
  'nopaging' => true,
) );

if ( $connected->have_posts() ) :
	echo '<div class="simple-byline-translations"><em>Translation</em>: ';
	$langcounter = 0;
	while ( $connected->have_posts() ) : $connected->the_post(); 
		$transintro = 'Read in English:';
		$langs = get_the_terms( $post->ID, 'intl_languages' );
		if ( $langs && !is_wp_error( $langs ) ) : 
			$langs_links = array();
			foreach ( $langs as $lang ) {		
				if ($lang->slug == 'spanish') { $transintro = 'Leer en espa?ol'; }
				if ($lang->slug == 'german') { $transintro = 'Lesen Sie auf Deutsch'; }
				if ($lang->slug == 'chinese') { $transintro = '点击查看本文中文版'; }
				if ($lang->slug == 'portuguese') { $transintro = 'Leia em português'; }
				if ($lang->slug == 'polish') { $transintro = 'Przeczytaj ten artyku? po polsku'; }
				// add more languages here as we publish translations
			}
			$langcounter++;
		endif;
		if ( !$langs ) : 
			$transintro = 'Read in English ';
			$langcounter++;
		endif;	
		?>
	    <a style="color: #333; font-weight: bold;" href="<?php the_permalink(); ?>"><?php if ($langcounter > 1) { echo ' / '; } ?><?php echo $transintro; ?><?php // the_title(); ?></a>
	<?php endwhile;
	echo '</div>';
wp_reset_postdata();
endif;

Admittedly, my wp_posts table is large — 1 GB in size, ~30K rows. But here’s my question: Is this something that is just doomed, running both sides of a Posts2Posts connection on a large database table? Or is there some way I could change this code to make it not melt my server? Thanks!