Agreed. This is a limitation we ran into trying to implement a critical accounting ledger on top of DynamoDB. The transaction model we came up with is formally verified w/ TLA+. We're turning our work into a product: txlayer.com
A fair question, and we’ve done it this way before at simple.com. When looking at the options for a pay-per use database, with global replication, streams and managed for you; We felt that if you could build a ledger on dynamo for these use cases, it’d be pretty compelling and fun.
