Primary Keys

Primary Keys Overview

At its core, primary keys 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 primary keys 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, PutCommand } from '@aws-sdk/lib-dynamodb';

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

// reuse docClient across the module for efficient, typed access
await docClient.send(new PutCommand({ TableName: 'Orders', Item: { pk: '1' } }));

The DynamoDBDocumentClient maps plain JavaScript objects to DynamoDB item format for you.

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

Amazon DynamoDB Cheatsheet

Handy DynamoDB (AWS SDK v3) reference related to primary keys.

How Primary Keys Works in DynamoDB

Primary Keys 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.

The DynamoDBDocumentClient maps plain JavaScript objects to DynamoDB item format for you.

• 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 Primary Keys

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

Common Mistakes

• Skipping error handling and edge cases when wiring up primary keys.
• Leaving primary keys untested, so regressions slip into production.
• Over-engineering primary keys before you actually need the extra flexibility.
• Ignoring documentation, which makes primary keys hard for the next developer to change.

Key Takeaways

• Primary Keys is a core part of working effectively with DynamoDB.
• Start small and keep primary keys focused on a single responsibility.
• Apply consistent patterns so primary keys scales across your project.
• Test and document primary keys to keep it maintainable over time.