Dynomo db now supports on-demand scaling which will be a handy option if you can’t predict the read/write capacity upfront. https://aws.amazon.com/about-aws/whats-new/2018/11/announcing-amazon-dynamodb-on-demand/
It is useful, but it is not a magic solution.
As the designer/engineer you still need to calculate and predict the range of CU levels that you will need for upper and lower peaks of your workload, and determine the range that you want to allow for.
Plus, systems configured to deliver high CU levels, can perform poorly when the CU level is reduced to a lower level.
As the designer you need to understand this process and be certain that the system is designed to perform properly at all setting between the high and low values.
Certainly take time to learn how to use it, but don’t assume that you can absolve yourself of responsibility for key, index and the CU design.
Moderator & Coach