The rich data types are also useful for partial updates, like adding items to a set, updating some fields in a map etc.

That does sound useful.

So I can have a key and an associated map and update a few members of the map?

I would like to learn how to do that.

Yep! Here's the AWS documentation about this feature: https://docs.aws.amazon.com/amazondynamodb/latest/developerg....

The rich data types can be useful for filtering, I guess? When you are running a query against a certain hash key and want the first record (sorted by range key) that meets a condition placed on a nested property of a map or whose "tags" property is a string set containing a certain member, for example.