Read and Write Capacity Units

Read and Write Capacity Units Overview

At its core, read and write capacity units is about doing one thing well inside your DynamoDB project. Once you understand the pattern, you can apply it consistently across features and teams.

Good read and write capacity units pays off across the whole codebase: fewer surprises, easier testing, and smoother onboarding. The snippet below is a solid starting point.

import { DynamoDBClient } from '@aws-sdk/client-dynamodb';
import { DynamoDBDocumentClient, GetCommand } from '@aws-sdk/lib-dynamodb';

const client = new DynamoDBClient({});
const docClient = DynamoDBDocumentClient.from(client);

const { Item } = await docClient.send(new GetCommand({
  TableName: 'Orders',
  Key: { pk: 'ORDER#123', sk: 'META' },
}));

GetCommand fetches a single item by its full primary key.

Read and Write Capacity Units Example

import { DynamoDBClient } from '@aws-sdk/client-dynamodb';
import { DynamoDBDocumentClient } from '@aws-sdk/lib-dynamodb';

const docClient = DynamoDBDocumentClient.from(new DynamoDBClient({}));
// docClient.send(new PutCommand(...)) etc.

• Start from a minimal Read and Write Capacity Units example and grow it only as needed.
• Keep configuration explicit so Read and Write Capacity Units behaves the same in every environment.
• Name things clearly so teammates understand your Read and Write Capacity Units at a glance.
• Add tests around Read and Write Capacity Units early to lock in expected behaviour.

Amazon DynamoDB Cheatsheet

Handy DynamoDB (AWS SDK v3) reference related to read and write capacity units.

How Read and Write Capacity Units Works in DynamoDB

Read and Write Capacity Units builds on DynamoDB's key-value and document model, where every item lives in a partition chosen by its partition key and is optionally ordered by a sort key.

GetCommand fetches a single item by its full primary key.

• Design access patterns first, then model keys around them.
• Prefer Query over Scan for predictable performance.
• Use expressions to read and write only what you need.
• Keep items small and avoid hot partitions.

Practical Guidance for Read and Write Capacity Units

In production, read and write capacity units should be cost-aware and resilient. Right-size capacity, handle throttling with retries, and lean on indexes to support your query patterns.

Common Mistakes

• Copying read and write capacity units snippets without understanding what each line does.
• Skipping error handling and edge cases when wiring up read and write capacity units.
• Leaving read and write capacity units untested, so regressions slip into production.
• Over-engineering read and write capacity units before you actually need the extra flexibility.

Key Takeaways

• Read and Write Capacity Units is a core part of working effectively with DynamoDB.
• Start small and keep read and write capacity units focused on a single responsibility.
• Apply consistent patterns so read and write capacity units scales across your project.
• Test and document read and write capacity units to keep it maintainable over time.