Keep hashed directories consistent in a load balanced server environment with Craft CMS 3

load-balancer-app.php

<?php
/**
 * Yii Application Config
 *
 * Edit this file at your own risk!
 *
 * The array returned by this file will get merged with
 * vendor/craftcms/cms/src/config/app/main.php and [web|console].php, when
 * Craft's bootstrap script is defining the configuration for the entire
 * application.
 *
 * You can define custom modules and system components, and even override the
 * built-in system components.
 */

/**
 * AdminCP resources in Craft CMS 3 are published in the public @webroot/cpresources 
 * with a directory name that's a hashed from the directory path and the timestamp
 * of when the resource was published.
 *
 * On load balanced environments, the addition of a timestamp can cause 404s as
 * the timestamp will vary from server to server. You can work around this problem
 * by providing your own `hashCallback` function to generate a hash of the directory
 * path without a timestamp.
 *
 * The `hashCallback` can actually be any PHP callable, but here it's presented
 * as an anonymous function. c.f.:
 *
 * vendor/craftcms/cms/src/config/app.web.php
 * vendor/craftcms/cms/src/web/AssetManager.php
 *
 * @author    nystudio107
 * @package   n/a
 * @since     1.0.0
 */
return [
    // All environments
    '*' => [
    ],

    // Live (production) environment
    'live'  => [
        'components' => [
            'assetManager' => function() {
                $generalConfig = Craft::$app->getConfig()->getGeneral();
                $config = [
                    'class' => craft\web\AssetManager::class,
                    'basePath' => $generalConfig->resourceBasePath,
                    'baseUrl' => $generalConfig->resourceBaseUrl,
                    'fileMode' => $generalConfig->defaultFileMode,
                    'dirMode' => $generalConfig->defaultDirMode,
                    'appendTimestamp' => true,
                    'hashCallback' => function ($path) {
                        return hash('md4', $path);
                    }
                ];
                return Craft::createObject($config);
            },
        ],
    ],

    // Staging (pre-production) environment
    'staging'  => [
    ],

    // Local (development) environment
    'local'  => [
    ],
];

Posted issue here: craftcms/cms#2712