Using cloud function to denormalize firestore data issue

Question

I am using many cloud function trigger and admin sdk to do multi-path update.I don't want to do too much multi-path update in client cause it will make firestore rules very complex and firestore rules also have document access call limits.So I decide to using cloud function to do most denomorlization stuff.

There is how one of my function work.

1. cloud function triggered at profiles/{userId}
2. and i using .get to load multi-path update needed paths at profilesPaths/{userId}
3. set writebatch.update on those paths
4. writebatch.commit()

And I think there have a problem.cloud function is asynchronous right?.So when function are running to step 3 And at the same moment a client delete one of update path from cf already loaded document at profilesPaths/{userId} (already loaded at step 2).and now cloud function loaded document is not the latest version.Will this happend? or i should using transactions to lock those documents?

Answer 1

Yes, Cloud Functions run asynchronous, and possibly in parallel. You should be using transactions to make sure that updates are consistent among all the clients that are trying to modify them concurrently.