I wouldn't know. I use DynamoDB almost exclusively. These simply aren't considerations that occur with that product.

It is true that it can be hard to size workloads into lambdas rather unusual CPU configuration; however, the real beauty of lambda is, you can just fork several parallel copies of your function. We can sometimes fork up to 250 instances just for a single "job."

If you're in the same boat we are where your workloads parallelize easily then Lambda has been incredibly cost effective for this use case.