title: Does AWS S3 Have a concept of files being 'updated'?
body: <p>I'd like to write a Lambda function that is triggered when files are added or modified in an s3 bucket and processes them and moves them elsewhere, clobbering older versions of the files.</p>
  
  <p>I'm wondering if AWS Lambda can be configured to trigger when files are updated?</p>
  
  <p>After reviewing the <a href="http://boto3.readthedocs.io/en/latest/reference/services/s3.html#bucket" rel="noreferrer">Boto3 documentation</a> for s3 it looks like the only things that could happen in a s3 bucket would be creations and deletions. </p>
  
  <p>Additionally, the <a href="http://docs.aws.amazon.com/lambda/latest/dg/invoking-lambda-function.html#supported-event-source-s3" rel="noreferrer">AWS documentation</a> seems to indicate there is no way to trigger things on 'updates' to S3. </p>
  
  <p>Am I correct in thinking there is no real concept of an 'update' to a file in S3 and that an update would actually be when something was destroyed and recreated? If I'm mistaken, how can I trigger a Lambda function when an S3 file is changed in a bucket?</p>