A big +1 for DynamoDB + S3 for a cash strapped startup. If you are writing an app from scratch, and the cost of data services is a big concern, then don't pick

A big +1 for DynamoDB + S3 for a cash strapped startup. If you are writing an app from scratch, and the cost of data services is a big concern, then don't pick a data store with complex and expensive replication properties. DynamoDB is admittedly harder to understand and use than Postgres or Mongo, but when you figure it out its a HTTP data API with no setup or maintenance costs. $8/mo of DynamoDB can easily cover your users and other CRUD.