Except that on S3 upload there will be only three attempts to execute Lambda, and then it will give up. I can easily imagine a simple outage that will lead to t

Except that on S3 upload there will be only three attempts to execute Lambda, and then it will give up. I can easily imagine a simple outage that will lead to three errors in a row, and the S3 files goes unaccounted. You're far better of sending out an SNS or an SQS triggered by an S3 object creation event.