If you want to use Ext.require you will need to create your application within the Ext.onReady listener:
Ext.require('MyApp.configuration.elastic');
Ext.onReady(function(){
Ext.create('MyApp.Application');
});
Alternatively, this should also work as it will make your application's main class require the config class:
Ext.define('MyApp.Application', {
requires: ['MyApp.configuration.elastic'],
// ...
});