db-config.php

<?php
/**
 * HyperDB configuration file
 *
 * This file should be installed at ABSPATH/db-config.php
 *
 * $wpdb is an instance of the hyperdb class which extends the wpdb class.
 *
 * Fully documented config file:
 * http://plugins.svn.wordpress.org/hyperdb/trunk/db-config.php
 */

/**
 * Basic Master/Slave server setup
 */
$wpdb->add_database(array(
	'host'     => DB_HOST,     // If port is other than 3306, use host:port.
	'user'     => DB_USER,
	'password' => DB_PASSWORD,
	'name'     => DB_NAME,
));

$wpdb->add_database(array(
	'host'     => DB_SLAVE,     // If port is other than 3306, use host:port.
	'user'     => DB_USER,
	'password' => DB_PASSWORD,
	'name'     => DB_NAME,
	'write'    => 0,
	'read'     => 1,
	'dataset'  => 'global',
	'timeout'  => 0.2,
));