how are you?
I have a flow that at times will need to send at least 1 million messages (in this case emails).
Today there is a transactional api where I can send up to 2000 (500 with attributes) at the same time.
There is also an automation studio where I can send a csv with more records at a time.
My question is whether with this volume the transactional API would serve well or is it time to go to automation studio?
If there is a better way, could you let me know?
For these high volumes, I will recommend pushing a CSV file to SFMC via SFTP (alternatively S3, Azure or Google Cloud Storage). Using SFTP will allow you to instantly trigger an automation, which will load the file into a data extension, and send an email to all the recipients in there.
This is IMHO more robust than relying on the Transactional API, as you here would need to keep track on which records have been triggered, and in case something goes wrong, you will need to resume the process from that point. This can only be done in your source system, since SFMC doesn't know at this point which data it hasn't received.
Also, keep in mind there are limitations on how many API calls you can perform. So if there are good alternatives which can save you calls, I would for sure recommend looking into these.
