function bbp_forum_query_last_reply_id( $forum_id = 0, $topic_ids = 0 ) {

	// Validate forum
	$forum_id = bbp_get_forum_id( $forum_id );

	// Get topic ID's if none were passed
	if ( empty( $topic_ids ) ) {
		$topic_ids = bbp_forum_query_topic_ids( $forum_id );
	}

	$query = new WP_Query( array(
		'fields'           => 'ids',
		'suppress_filters' => true,
		'post_parent__in'  => $topic_ids,
		'post_status'      => bbp_get_public_status_id(),
		'post_type'        => bbp_get_reply_post_type(),
		'posts_per_page'   => 1,
		'orderby'          => array(
			'post_date' => 'DESC',
			'ID'        => 'DESC'
		),

		// Performance
		'update_post_term_cache' => false,
		'update_post_meta_cache' => false,
		'ignore_sticky_posts'    => true,
		'no_found_rows'          => true
	) );

	$reply_id = array_shift( $query->posts );

	unset( $query );

	// Filter & return
	return (int) apply_filters( 'bbp_forum_query_last_reply_id', $reply_id, $forum_id );
}