This will sound flippant, but that's not what Dynamo is for. If you want to do freeform relational queries like that then put it in a relational database.

Dynamo is primarily designed for high volume storage/querying on well understood data sets with a few query patterns. If you want to be able to query information on employees based on their name and city you'll need to build another index keyed on name and city (in practice Dynamo makes that reasonably simple by adding a secondary index).