How to create multiple DynamoDB entries under the same primary key?
you cannot create multiple entries with same primary key. Please create composite keys (multiple keys together as primary key). Please note you cannot have multiple records of same combination
I am developing a skill for Amazon Alexa and I'm using DynamoDB for storing information about the users favorite objects. I would like 3 columns in the database:

Alexa userId
Object
Color

I currently have the Alexa userId as the primary key. The problem that I am running into is that if I try to add an entry into the db with the same userId, it overwrites the entry already in there. How can I allow a user to have multiple objects associated with them in the db by having multiple rows? I want to be able to query the db by the userId and receive all the objects that they have specified. 
If I create a unique id for every entry, and there are multiple users, I can't possibly know the id to query by to get the active users' objects.