title: S3 last-modified timestamp for eventually-consistent overwrite PUTs
body: <p>The AWS S3 docs state that:</p>
  
  <blockquote>
    <p>Amazon S3 offers eventual consistency for overwrite PUTS and DELETES in all regions.</p>
    
    <p><a href="http://docs.aws.amazon.com/AmazonS3/latest/dev/Introduction.html#ConsistencyModel" rel="noreferrer">http://docs.aws.amazon.com/AmazonS3/latest/dev/Introduction.html#ConsistencyModel</a></p>
  </blockquote>
  
  <p>The timespan until full consistency is reached can vary. During this period GET requests may return the previous object or the udpated object.</p>
  
  <p>My question is: </p>
  
  <p>When is the last-modified timestamp updated? Is it updated immediately after the overwrite PUT succeeds but <em>before</em> full consistency is reached, or is it only updated after full consistency is achieved?</p>
  
  <p>I suspect the former but I can't find any documentation which clearly states this.</p>