Reference Architecture: DDB Single-Table Design

This set of data models comes from Alex DeBrie's 2019 re:Invent talk "Data modeling with Amazon DynamoDB (CMY304)"

To Deploy and Run

First, do whatever is necessary to have CLI access to your AWS account (you can quickly verify this with aws s3 ls or similar). The serverless file does nothing else but create the DynamoDB table.

$ npm ci

$ npx sls deploy

$ npm run test:int

E-Commerce Store

Alex describes some data access patterns in his talk that I've listed below, with one minor modification. Pattern #3 originally was "Get single order and order items" and I have modified it to "Get all order items for an order". This keeps data access in line with a REST or GraphQL framework, which is 99% of my building experience.

Access Patterns

1. Get a user profile
2. Get an order
3. Get orders for user
4. Get order items for order
5. Get orders for user by status
6. Get (first few) placed orders

ERD

Entity Chart

Below is how each primary key is mapped for each entity:

	PK	SK	GSI1PK	GSI1SK	GSI2PK	GSI2SK	GSI3PK
User	USER#<username>	#PROFILE#<username>
User Address	N/A	N/A
Order	USER#<username>	ORDER#<orderId>	SK	PK	PK	<status>#<createdAt>	<random_hash>
Order Item	ITEM#<itemId>	ORDER#<orderId>	SK	PK

Access Pattern Solved

	Access Pattern	Query Conditions
1	Get user profile	GET PK = USER#<username> AND SK = #PROFILE#<username>
2	Get order by id	QUERY GSI1PK = ORDER#<orderId> AND GSI1SK BeginsWith(USER#)
3	Get orders for user	QUERY PK = USER#<username> AND SK BeginsWith(ORDER#)
4	Get order items for order	QUERY GSI1PK = ORDER#<orderId> AND SK BeginsWith(ITEM#)
5	Get orders for user by status (e.g., 'SHIPPED')	QUERY GSI2PK = USER#<username> AND GSI2SK BeginsWith('SHIPPED#')
6	Get top 3 placed orders	SCAN GSI3PK LIMIT 3

Architecture

This project models how to implement single-table-design patterns. As such, it needs nothing higher than a Repository layer. The repo pulls in models defined in a separate file. The models file is mostly key schema mapping for dynamodb-toolbox so it can do the heavy lifting for us.