title: Mongoose OR operator for optional document
body: <pre><code>Jobs.find({status: 'active', expiry_date: {$gt: Date.now()}}, function(err, result) {})
  </code></pre>
  
  <p>I have above query that find active status and not expired. The logic just worked but it's broken for Jobs that doesn't have expiry_date document. This is due to the expiry_date document is a later added requirement.</p>
  
  <p>How to still return the active Jobs if the expiry_date document not present? </p>