Order By and Group By in Google Datastore Node JS

I am trying to write a datastore query in NodeJS.

I want to order by timestamp but also only distinct unique ID's (no duplicates) and only retrieve the latest datastore item for each unique ID.

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For example

USER_ID - TIMESTAMP
10      - 1000
10      - 500
5       - 10
5       - 1500
5       - 50

I want the query to result with

USER_ID - TIMESTAMP
10      - 1000
5       - 1500

---

What I've tried:

datastore.createQuery('example')
  .groupBy('USER_ID')
  .order('USER_ID')
  .order('TIMESTAMP')

But it returns the data ordered by USER_ID, not TIMESTAMP

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