For explicitness & searchability, commenting with the title of this talk, which is indeed excellent, not limited to DynamoDB, and which was kind of a revelation after years of using DynamoDB suboptimally:

Rick Houlihan - AWS re:Invent 2018: Amazon DynamoDB Deep Dive: Advanced Design Patterns for DynamoDB (DAT401) , https://www.youtube.com/watch?v=HaEPXoXVf2k

It should be watched along with reading the associated doc: https://docs.aws.amazon.com/amazondynamodb/latest/developerg...