The problem: you write files to an S3 bucket on Amazon Web services. Maybe a single user/process does this, maybe multiple users or processes do this. But you want to keep a particular process from going rogue and deleting your data. What do you do?
The answer: You write a function in AWS Lambda that is fired whenever something is uploaded to the S3 bucket in question. It then calls the copyObject() method and makes a copy of the file to another bucket--one that only it (and your admin account, presumably) have access to write to.
The GitHub repository is at:
It's a quick and dirty thing that I put together mostly as a demo of how to integrate AWS Lambda with other S3 services.