Firestore -- Get Only The Changed Documents In A Large Synced Collection

I've read all of the questions below, and cannot find anything in the docs to describe how to sync a collection and receive only changed documents from a collection. I've got over

Solution 1:

Firestore queries don't have a notion of querying "only things that have changed". You will need to create that notion on your own. The usual way to do this is by recording a timestamp in each document with the time it was last updated, then using that field in a range filter to get only documents updated since the latest update was received. You will need to track that latest update timestamp in the client. One possibility is to use the greatest timestamp seen in any document to date.

Solution 2:

This is a great article explaining some tips.

A strategy here is to add a property on each document such as lastModified and .get() from the Firebase client cache and only query the server to get documents with a lastModified greater than the client cache document fetch timestamp.

https://medium.com/firebase-tips-tricks/how-to-drastically-reduce-the-number-of-reads-when-no-documents-are-changed-in-firestore-8760e2f25e9e