title: How to get documents that were updated in the last hour from firestore?
body: <p>I am trying to implement full text search of firestore DB by using Elasticsearch.</p>
  
  <p>In order to sync the firestore data to elasticsearch, I used cloud functions with Firestore update events, such that whenever a firestore document is updated, a cloud function is triggered which updates the elasticsearch.</p>
  
  <p>This works as expected. However, this is not cost effective.</p>
  
  <p>I would like to update the elasticsearch periodically every hour by querying the firestore DB for documents that changed in the last one hour and updating elasticsearch.</p>
  
  <p>Is there a way to query firestore for only those documents that got updated in the last hour?</p>