I have a situation where I would like to update custom object records in Sales Cloud as emails to associated contacts are sent in Marketing Cloud (so a different record is updated for each email message sent). The send's audience is a data extension that contains the custom object record IDs for each recipient. So, I can theoretically use a bit of AMPScript in the email and the UpdateSingleSalesforceObject function to do this. But my question is: how well will this scale when we do sends of 50,000-100,000 or more messages?
Does UpdateSingleSalesforceObject cache updates until the whole send is done, and only process them then? Does it send data to Sales Cloud in batches? Or is it actually okay to send 100,000+ record updates in a stream back through the Connector as the send happens? How much will this slow down my sends?
Just wondering if anyone has done this at any sort of scale, and how well it works; or if there are alternatives folks here would recommend that don't involve expensive middleware or a lot of moving parts. Thank you in advance!