bp_messages_clear_cache_on_message_delete( int|array $thread_ids, int $user_id )

function bp_messages_clear_cache_on_message_delete( $thread_ids, $user_id ) {
	// Delete thread and thread recipient cache.
	foreach( (array) $thread_ids as $thread_id ) {
		// wp_cache_delete( $thread_id, 'bp_messages_threads' );
		bp_messages_delete_thread_paginated_messages_cache( $thread_id );
		wp_cache_delete( "thread_recipients_{$thread_id}", 'bp_messages' );
	}

	// Delete unread count for logged-in user.
	wp_cache_delete( $user_id, 'bp_messages_unread_count' );
}