When using aliases for zero downtime deployments, is there a way to know through the api when the indexing of the new collection/s is complete so that the alias can be updated to point to the new collection and the old one can be deleted?

How are you populating the new collection? Via import api?

Yes, a script that GitHub actions runs if there are changes to the migrations folder for the sql database

You can check the document count on the collection you just imported and if the count looks good, you can switch.

So basically snapshot each collection that has changed, snapshot doc count and then periodically check when the new collections have reached the snapshotted count to swap to them?

Actually, if your imports finish and you are able to hit the

/health

API successfully that should be enough to do a swap for small to medium sized collections.