title: MongoDB: is it possible to capture TTL events with Change Stream to emulate a scheduler (cronjob)?
body: <p>I'm new to MongoDB and I'm looking for a way to do the following:</p>
  
  <p>I have a collection of a number of available "things" to be used.
  The user can "save" a "thing" and decrement the number of available things. 
  But he has a time to use it before it expires. 
  If it expires, the thing has to go back to the collection, incrementing it again.</p>
  
  <p>It would be ideal if there was a way to monitor "expiring dates" in Mongo. But in my searches I've only found a TTL (time to live) for automatically deleting entire documents.</p>
  
  <p>However, what I need is the "event" of the expiration... Than I was wondering if it would be possible to capture this event with Change Streams. Then I could use the event to increment "things" again.</p>
  
  <p>Is it possible or not? Or would there be a better way of doing what I want?</p>