Dynamodb

Amazon DynamoDB

DynamoDB is a fully managed, serverless, key-value NoSQL database designed to run high-performance applications at any scale (Single-digit millisecond latency).

When to Use

• Serverless Apps: The default DB for AWS Lambda.
• Infinite Scaling: Handles petabytes of data without maintenance.
• Shopping Carts / Sessions: High throughput, simple key access.

Quick Start (AWS SDK v3)

import { DynamoDBClient, PutItemCommand } from "@aws-sdk/client-dynamodb";

const client = new DynamoDBClient({});
const command = new PutItemCommand({
  TableName: "Users",
  Item: {
    PK: { S: "USER#123" },
    SK: { S: "PROFILE" },
    Name: { S: "Alice" },
  },
});
await client.send(command);

Core Concepts

Partition Key (PK) & Sort Key (SK)

• PK: Determines which partition holds the data. Must be unique unless SK is present.
• SK: Sorts items with the same PK.
• Composite Key: PK + SK together form the primary ID.

Single Table Design (The "OneTable" Pattern)

Storing multiple entity types (Users, Orders) in one table to enable pre-joining data via item collections. (Less strictly required now, but still common).

Provisioned vs On-Demand

• On-Demand: Pay per request. Good for spiky/unknown loads.
• Provisioned: Pay for capacity. Cheaper for predictable loads.

Best Practices (2025)

Do:

• Access Patterns First: Design your schema based on how you will query the data. You cannot easily add arbitrary queries later.
• Use GSI (Global Secondary Index): To query by non-key attributes.
• Use TTL: To verify old items are deleted automatically (free delete).

Don't:

• Don't Scan: Scan reads the entire table. It is slow and expensive. Always Query.
• Don't store large blobs: 400KB limit per item. Store large data in S3 and save the link in Dynamo.

References

• DynamoDB Developer Guide