title: How to migrate GAE alias to new application without migrating data
body: <p>We have an existing application using the legacy Master-Slave database with an alias to one of our subdomains.  When we went to HRD, we re-engineered the application considerably and so we don't want to use the migration tool.  In fact, we don't care about the data at all (see <strong>background</strong> below for why).  I just want to change the alias so that the subdomain points to a new application, or in other words:</p>
  
  <p>subdomain.example.com --> oldapplication.appspot.com</p>
  
  <p>to </p>
  
  <p>subdomain.example.com --> newapplication.appspot.com</p>
  
  <p>Ordinarily (in a non-GAE environment) this would be a simple DNS change and once DNS propagates we could shut down the legacy application.  In GAE, we can delete the old alias and set the alias up on the new application, but we don't know how long this is going to take to complete (other than the 10 seconds it takes for someone to click the buttons and post to the control panel).  We're potentially willing to accept a very small window of downtime where subdomain.example.com won't be serving pages (because we know when peak loads are).  But does anyone know how long this change-over should take?</p>
  
  <p>We reported a production issue but have not had any feedback.</p>
  
  <p><strong>Background:</strong>
  This application serves a bit of Javascript that can be embedded in parters' web sites.  The data for this gets fed from our main site (not on GAE) via an API on a daily basis.  So we don't care about migrating data and in fact we're already doing the daily feed to the new application and just need to change the alias.</p>