AWS S3 has a great, but little known functionality: You can request metadata about the content of the bucket in XML. This makes it a great storage space for all kinds of batch oriented applications. No need for a self-written API.

Requesting the metadata is easy, it's just a GET request to the root of the buckets' URL: http://[bucket_name].s3.amazonaws.com/

The response will look like this:

<ListBucketResult>
  <Name>your-bucket-name</Name>
  <Prefix/>
  <Marker/>
  <MaxKeys>1000</MaxKeys>
  <IsTruncated>false</IsTruncated>
  <Contents>
    <Key>your_filename.json</Key>