I'm using Mongo change streams to send database changes in realtime from my node backend to an angular webapplication.

When I mutate a lot of data rows using a transaction, I want to send those changes to the client as one accumulated change and not one by one.

To achive that, I queue new changes if they are part of a transaction.

And here starts my problem:

How to identify the last change event of a transaction? At the moment I set a timeout and wait if another change with the same lsid arrives within the timeout. If not I consider the transaction complete.

Aside from being a very ugly hack, this has two severe downside:

• If the timeout is too short, I can't rely on the transaction changes to arrive fast enough
• The timeouts accumulate and lead (in case of transactions affecting a lot of documents) to very high response times on the client side

I think the best solution would be to either set a flag on the change event (something like a "last" or "finished" boolean in addition to the lsid) or emit a specific event in the stream after a transaction's last change.

If anybody has already solved that issue in another fashion, please let me know.

Thanks very much!