You can really do either with S3- it's just an eventually consistent, immutable kv. A) Keep a consistent manifest of chunk range to keys. B) Keep a ordered lis

You can really do either with S3- it's just an eventually consistent, immutable kv. A) Keep a consistent manifest of chunk range to keys. B) Keep a ordered list of keys that represent the DAG. In case A, you'll be able to assemble your blob in parallel even.