DynamoDB

Overview

MBC CQRS Serverless uses DynamoDB as its primary data store, implementing CQRS and Event Sourcing patterns through a structured table design. Understanding the table structure is essential for building efficient applications.

Table Architecture

In the MBC CQRS Serverless, DynamoDB tables are organized into the following types:

Entity Tables

Table Type	Naming Convention	Purpose
Command Table	entity-command	Stores write commands (write model)
Data Table	entity-data	Stores current state (read model)
History Table	entity-history	Stores all versions for event sourcing

System Tables

Table	Purpose
tasks	Stores information about long-running asynchronous tasks
sequences	Holds sequence data for ID generation

Table Definition

Table definitions are stored in the prisma/dynamodbs folder. To add a new entity table:

Step 1: Define Table in Configuration

Add the table name to prisma/dynamodbs/cqrs.json:

["cat", "dog", "order"]

Step 2: Run Migration

For local development:

# Migrate DynamoDB tables only
npm run migrate:ddb

# Migrate both DynamoDB and RDS
npm run migrate

Key Design Patterns

Standard Key Structure

All tables use a composite primary key consisting of:

Key	Format	Example
pk	TYPE#tenantCode	ORDER#ACME
sk	TYPE#code	ORDER#ORD-000001

Entity Key Examples

// Order entity
const orderKey = {
  pk: `ORDER#${tenantCode}`,
  sk: `ORDER#${orderId}`,
};

// User entity
const userKey = {
  pk: `USER#${tenantCode}`,
  sk: `USER#${userId}`,
};

// Hierarchical data (e.g., organization)
const departmentKey = {
  pk: `ORG#${tenantCode}`,
  sk: `DEPT#${parentId}#${deptId}`,
};

Table Attributes

Common Attributes

All entity tables share these common attributes:

Attribute	Type	Description
pk	String	Partition key
sk	String	Sort key
id	String	Unique identifier (pk#sk hash)
code	String	Business code
name	String	Display name
tenantCode	String	Tenant identifier
type	String	Entity type
version	Number	Version for optimistic locking
attributes	Map	Custom entity attributes
createdBy	String	Creator user ID
createdIp	String	Creator IP address
createdAt	String	Creation timestamp (ISO 8601)
updatedBy	String	Last modifier user ID
updatedIp	String	Last modifier IP address
updatedAt	String	Last update timestamp (ISO 8601)

Command-Specific Attributes

Attribute	Type	Description
source	String	Command source identifier
requestId	String	Request tracking ID

History-Specific Attributes

Attribute	Type	Description
seq	Number	Sequence number in history

Secondary Indexes

Adding Global Secondary Indexes

The default table configuration does not include GSIs. You can add them based on your query patterns. A common pattern is adding a code-index for fast lookups by business code:

Example GSI definition (add to your table configuration):

{
  "GlobalSecondaryIndexes": [
    {
      "IndexName": "code-index",
      "KeySchema": [
        { "AttributeName": "tenantCode", "KeyType": "HASH" },
        { "AttributeName": "code", "KeyType": "RANGE" }
      ],
      "Projection": { "ProjectionType": "ALL" }
    }
  ]
}

Example usage with custom GSI:

// Find entity by code (requires code-index GSI)
const params = {
  TableName: 'entity-data',
  IndexName: 'code-index',
  KeyConditionExpression: 'tenantCode = :tenant AND code = :code',
  ExpressionAttributeValues: {
    ':tenant': tenantCode,
    ':code': entityCode,
  },
};

Best Practices

Key Design

1. Keep partition keys broad: Distribute data evenly across partitions
2. Use hierarchical sort keys: Enable efficient range queries
3. Include tenant in partition key: Ensure data isolation

Query Optimization

1. Use Query over Scan: Always use partition key in queries
2. Limit result sets: Use pagination for large datasets
3. Project needed attributes: Only retrieve required fields

Capacity Planning

1. Use on-demand capacity: Recommended for unpredictable workloads
2. Monitor consumed capacity: Set up CloudWatch alarms
3. Consider DAX: For read-heavy workloads requiring microsecond latency

Local Development

DynamoDB Local

The framework includes DynamoDB Local for development:

# Start DynamoDB Local (included in docker-compose)
docker-compose up -d dynamodb-local

# Access DynamoDB Local Admin UI
open http://localhost:8001

Environment Variables

# Local DynamoDB endpoint
DYNAMODB_ENDPOINT=http://localhost:8000
DYNAMODB_REGION=ap-northeast-1

Related Documentation

• Key Patterns: Detailed key design strategies
• Entity Patterns: Entity modeling guidelines
• Sequence: Sequence ID generation
• CommandService: Command handling and data sync