How to keep two read only collection synced with mongoose

I have a mongoose model called Products which I feed from an external system (a google spreadsheet).

Every time the spreadsheet changes, I get an event and I need to find out what changed and update Products collection accordingly.

The easiest method I though about was:

1. On spreadsheet changed event, delete all documents in Product collection
2. Insert the entire new collection of products I got from the spreadsheet into Products collection again.

This is hardly efficient, but it's an easy and clean solution, assuming the collection is not very big and doesn't update too frequently.

Any other method I can think of involves iterating both the updated google spreadsheet and the Products collection and comparing them to each other.

Is there an inherited way of doing this ? perhaps a more efficient algo ?