Sometimes you don't need all stock rewrite rules

less-rewrite-rules.php

<?php
/*
Plugin Name: Less Rewrite Rules
Plugin URI: https://conversionready.com
Description: Less matching, more speed. Removes "attachment", "feed", "trackback" rewrites.
Author: Leho Kraav
Author URI: https://conversionready.com
Version: 2015.05.01
License: MIT
*/

register_activation_hook( __FILE__, [ "Plugin_Less_Rewrite_Rules", "activate" ] );
register_deactivation_hook( __FILE__, [ "Plugin_Less_Rewrite_Rules", "deactivate" ] );

final class Plugin_Less_Rewrite_Rules {
    private static $instance;
    private static $flag;
    private static $match_rules = [ "attachment", "feed", "trackback" ];

    function __construct() {
        static::$flag = __CLASS__ . "_flush";

        add_action( "wp_loaded", [ __CLASS__, "init" ] );
    }

    public static function activate() {
        if ( ! get_option( static::$flag ) ) {
            add_option( static::$flag, true );
        }
    }

    # plugin does a full run before deactivation, must flush without filter
    public static function deactivate() {
        remove_filter( "rewrite_rules_array", [ __CLASS__, "less_rewrite_rules" ] );
        flush_rewrite_rules();
    }

    # rewrite rules must be filtered at all times
    public static function init() {
        add_filter( "rewrite_rules_array", [ __CLASS__, "less_rewrite_rules" ] );

        # http://www.andrezrv.com/2014/08/12/efficiently-flush-rewrite-rules-plugin-activation/
        if ( get_option( static::$flag ) ) {
            flush_rewrite_rules();
            delete_option( static::$flag );
        }
    }

    # https://codex.wordpress.org/Plugin_API/Filter_Reference/rewrite_rules_array
    # ensure empty object cache, when debugging rewrite rule database issues
    public static function less_rewrite_rules( $rules ) {
        foreach ( $rules as $rule => $rewrite ) {
            foreach ( static::$match_rules as $match ) {
                if ( strpos( $rule, $match ) || strpos( $rewrite, $match ) ) {
                    unset( $rules[ $rule ] );
                }
            }
        }

        return $rules;
    }

    public static function get_instance() {
        return self::$instance ? self::$instance : new self;
    }
}

Plugin_Less_Rewrite_Rules::get_instance();