Pardon my ignorance but I was hung up on this line. > Out-of-sync document stores could lead to subtle bugs, such as a document being present in one store but

Pardon my ignorance but I was hung up on this line. > Out-of-sync document stores could lead to subtle bugs, such as a document being present in one store but not another. But then the article suggests to upload synchronously in S3/DDB and then sync asynchronously to actual document stores. How does this solve out of sync issue? It doesn't. It can't be solved is what I'm thinking. > Data, numbers How much data are we talking about?