[garethmcc]

Autoscaling is monstrously good on DynamoDB. You can turn on on demand mode so that it will scale up to the sheer limits of DynamoDB itself, but you pay per usage. So if you do want to set some kind of limit based on affordability you can set limits as to how much the tables scale.

As to how that autoscaling performs, its instant and always available so you have nothing to worry about there. Rather spend your time focussed on optimisation of queries than managing the scalability of your datastore which is as it should be.