Update post_modified on _bbp_last_active_time update, to improve order efficiency

bbpress-improvment.php

<?php
add_action( 'updated_post_meta', 'update_post_modified_on__bbp_last_active_time_update', 10, 4 );
function update_post_modified_on__bbp_last_active_time_update( $meta_id, $object_id, $meta_key, $_meta_value ) {
	if ( '_bbp_last_active_time' == $meta_key ) {
		$obj = get_post( $object_id );
		if ( 'topic' == $obj->post_type ) {
			$obj->post_modified = $_meta_value;
			$obj->post_modified_gmt = gmdate('Y-m-d H:i:s', strtotime( $_meta_value ) );
			wp_insert_post( $obj );
		}
	}
}

add_filter( 'pre_get_posts', 'willy_order_topics' );
function willy_order_topics( $q ) {
		if ( $q->get( 'post_type' ) == 'topic' ) {
			$q->set( 'orderby', 'modified' );
		}
	return $q;
}