I've writing bulk email script in node.js that uses Amazon SES.
The scripts divides a large list into queues and each queue is executed separately. For each queue I use a different connection (even though it's none blocking) since I'm waiting on the response before i proceed to the next email in the queue.
I can connect and send via amazon SES using their API or using SMTP. I would assume that both methods will keep the connection open for the entire queue.
I was wondering if one has any advantages over the other. Is there any advantage in performance in favor of the API or the SMTP?
Definitely use the HTTP API. SMTP protocol involves a lot of back and forth. That's why connections are pooled typically for transferring lots of messages over SMTP between the same two points.
Another advantage to using the HTTP API is you can use HTTPS between your program and Amazon SES.