title: MongoDB Change Streams events: replace vs update?
body: <p>I checked the document <a href="https://docs.mongodb.com/manual/reference/change-events/" rel="nofollow noreferrer">https://docs.mongodb.com/manual/reference/change-events/</a></p>
  
  <p>I'm not sure when exactly events "replace" and "update" happen.</p>
  
  <p>For example, when I use MongoDB Compass to change 1 field of a document, I expected that event "update" will fire, but when I logged the event, it's "replace".</p>
  
  <p>So if an expected update is actually a "replace" event, when will the real "update" event fire?</p>
  
  <p>Thanks.</p>