WP Core Scalability issue

class-wp-rewrite.php

		/**
	 * Retrieves the rewrite rules.
	 *
	 * The difference between this method and WP_Rewrite::rewrite_rules() is that
	 * this method stores the rewrite rules in the 'rewrite_rules' option and retrieves
	 * it. This prevents having to process all of the permalinks to get the rewrite rules
	 * in the form of caching.
	 *
	 * @since 1.5.0
	 * @access public
	 *
	 * @return array Rewrite rules.
	 */
	public function wp_rewrite_rules( $flushed = false ) {
		$this->rules = get_option('rewrite_rules');
		if ( $flushed === true ) {
			$this->matches = 'matches';
			$this->rewrite_rules();
			update_option('rewrite_rules', $this->rules);
		}

		return $this->rules;
	}
  
  /**
	 * Removes rewrite rules and then recreate rewrite rules.
	 *
	 * Calls WP_Rewrite::wp_rewrite_rules() after removing the 'rewrite_rules' option.
	 * If the function named 'save_mod_rewrite_rules' exists, it will be called.
	 *
	 * @since 2.0.1
	 * @access public
	 *
	 * @staticvar bool $do_hard_later
	 *
	 * @param bool $hard Whether to update .htaccess (hard flush) or just update rewrite_rules option (soft flush). Default is true (hard).
	 */
	public function flush_rules( $hard = true ) {
		static $do_hard_later = null;

		// Prevent this action from running before everyone has registered their rewrites.
		if ( ! did_action( 'wp_loaded' ) ) {
			add_action( 'wp_loaded', array( $this, 'flush_rules' ) );
			$do_hard_later = ( isset( $do_hard_later ) ) ? $do_hard_later || $hard : $hard;
			return;
		}

		if ( isset( $do_hard_later ) ) {
			$hard = $do_hard_later;
			unset( $do_hard_later );
		}

		//update_option( 'rewrite_rules', '' );
		$this->wp_rewrite_rules( true );

		/**
		 * Filters whether a "hard" rewrite rule flush should be performed when requested.
		 *
		 * A "hard" flush updates .htaccess (Apache) or web.config (IIS).
		 *
		 * @since 3.7.0
		 *
		 * @param bool $hard Whether to flush rewrite rules "hard". Default true.
		 */
		if ( ! $hard || ! apply_filters( 'flush_rewrite_rules_hard', true ) ) {
			return;
		}
		if ( function_exists( 'save_mod_rewrite_rules' ) )
			save_mod_rewrite_rules();
		if ( function_exists( 'iis7_save_url_rewrite_rules' ) )
			iis7_save_url_rewrite_rules();
	}