This article is already pretty outdated. According to Jim Scharf with DynamoDB On-Demand you don't really have to care anymore about DynamoDB's implementation details, like partitioning: https://twitter.com/jim_scharf/status/1069056907686465537
You might also want to read about the scaling behavior of DynamoDB On-Demand (https://docs.aws.amazon.com/amazondynamodb/latest/developerg...). Of course you can't immediately scale to any arbitrary request rate, but the way it's implemented sounds fine to me.
So do you have a source for your claim?