Firebase pagination using a timestamp/date as the orderBy - reactjs

Question

I am struggling to get pagination working when I use a date (firebase timestamp) to retrieve data.
This is basically what I do:
let jobsRef = db.collection("jobs")
.orderBy('createdAt', 'desc')
.limit(QUERY_LIMIT);
jobsRef = jobsRef.startAfter(this.props.jobs[this.props.jobs.length - 1].createdAt);
However it seems that i get returned items sometimes that I have just already received. I am guessing because of similar dates?
So how could I basically return a list of jobs ordered by createdAt and have an offset/limit (pagination)?
createdAt looks like the timestamp type: 23 October 2020 at 17:26:31 UTC+2
When I log createdAt however I see this: {seconds: 1603537477, nanoseconds: 411000000}
Maybe I should be storing createdAt as a unix timestamp? Or what is the ideal way to deal with this?
Here is how it looks in the database (popup when i click edit on createdAt):

Answer 1

If multiple documents can have the same value for the field you're sorting on, passing in a value for that field is not guaranteed to point to a unique document. So you indeed may be passing in an ambiguous instruction, leading to an unwanted result.
When possible, I highly recommend passing the entire document to the Firestore API. This leaves it up to Firestore to take the necessary data from that document to uniquely/unambiguously find the anchor for your query.
So instead of:
jobsRef.startAfter(this.props.jobs[this.props.jobs.length - 1].createdAt);
Do:
jobsRef.startAfter(this.props.jobs[this.props.jobs.length - 1]);

Answer 2

I was facings a similar problem, after may hours I finally found a solution, all you need to do is converting that number to firestore's Timestamp
import { Timestamp }. from #angular/fire/firestore;
let createdAt: number = 56772766688383;
let timestamp = Timestamp.fromMillis(createdAt);
//then pass that to startAfter
startAfter(timestamp)