As an alternative to #318 & #464, cortex could rely on the the new built-in DynamoDB autoscaling:

https://aws.amazon.com/about-aws/whats-new/2017/06/announcing-amazon-dynamodb-auto-scaling/

In practice this means a configuration option to table manager that prevents it from updating provisioned throughput whilst continuing to create new periodic tables.