title: MongoDB query for document older than 30 seconds
body: <p>Does anyone have a good approach for a query against a collection for documents that are older than 30 seconds. I'm creating a cleanup worker that marks items as failed after they have been in a specific state for more than 30 seconds.</p>
  
  <p>Not that it matters, but I'm using <a href="https://npmjs.org/package/mongojs" rel="nofollow">mongojs</a> for this one.</p>
  
  <p>Every document has a <code>created</code> time associated with it.</p>