I'm the author, and thanks for asking! The article is really just background, submitted by a friend. Still building the demo & documentation, so my apologies for the confusion.

Entity Manager is a framework for defining, managing, and most importantly QUERYING an entity model with DynamoDB. It's actually platform-generic, so the DynamoDB-specific machinery is implemented at https://github.com/karmaniverous/entity-client-dynamodb

Entity Manager's most important feature is that it permits a simple, scheduled partition sharding configuration and then transparent, multi-index querying of data across shards with a very compact, fluent query API.

This resolves the biggest challenge of using DynamoDB at scale, which is that very large data sets MUST be sharded, and a given query can ONLY operate against a single shard. If you're querying on the basis of a related record, you won't know which shard your results will be on so you must query ALL shards.

Entity Manager reduces this to an effortless operation: once you've defined your sharding strategy for a given entity, you can forget sharding is even a thing.

For some more color on Entity Manager within the context of SQL vs NoSQL databases, please review this (much shorter!) article: https://karmanivero.us/projects/entity-manager/sql-vs-nosql