title: Is MongoDB _id (ObjectId) generated in an ascending order?
body: <p>I know how the _id column contains a representation of timestamp when the document has been inserted into the collection. here is an online utility to convert it to timestamp: <a href="http://steveridout.github.io/mongo-object-time/" rel="noreferrer">http://steveridout.github.io/mongo-object-time/</a></p>
  
  <p>What I'm wondering is if the object id string itself is guaranteed maintain the ascending order or not? i.e. does this comparison always return true? </p>
  
  <p><code>"newest object id" &gt; "second newest object id"</code>  </p>