How to Use DynamoDB with Lambda: Simple Integration Guide

To use DynamoDB with Lambda, create a Lambda function with permissions to access DynamoDB, then use the AWS SDK inside the function to read or write data. This lets your Lambda respond to events and interact with DynamoDB tables easily.

Syntax

Here is the basic syntax to use DynamoDB in a Lambda function using the AWS SDK for JavaScript (v3):

• import the DynamoDB client and commands.
• Create a DynamoDB client instance.
• Use commands like PutItemCommand or GetItemCommand to write or read data.
• Call client.send(command) to execute the operation.

javascript

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

const client = new DynamoDBClient({ region: "us-east-1" });

// Example: Put item
const putParams = {
  TableName: "YourTableName",
  Item: {
    "PrimaryKey": { S: "key1" },
    "Attribute": { S: "value" }
  }
};
const putCommand = new PutItemCommand(putParams);
await client.send(putCommand);

// Example: Get item
const getParams = {
  TableName: "YourTableName",
  Key: {
    "PrimaryKey": { S: "key1" }
  }
};
const getCommand = new GetItemCommand(getParams);
const data = await client.send(getCommand);
console.log(data.Item);

Example

This example shows a Lambda function that writes a new item to DynamoDB and then reads it back. It uses async/await and the AWS SDK v3.

javascript

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

const client = new DynamoDBClient({ region: "us-east-1" });

export const handler = async (event) => {
  const tableName = "MySampleTable";
  const itemKey = "item123";

  // Write item
  const putParams = {
    TableName: tableName,
    Item: {
      "Id": { S: itemKey },
      "Message": { S: "Hello from Lambda!" }
    }
  };
  await client.send(new PutItemCommand(putParams));

  // Read item
  const getParams = {
    TableName: tableName,
    Key: {
      "Id": { S: itemKey }
    }
  };
  const data = await client.send(new GetItemCommand(getParams));

  return {
    statusCode: 200,
    body: JSON.stringify({ item: data.Item })
  };
};

Output

{"statusCode":200,"body":"{\"item\":{\"Id\":{\"S\":\"item123\"},\"Message\":{\"S\":\"Hello from Lambda!\"}}}"}

Common Pitfalls

Common mistakes when using DynamoDB with Lambda include:

• Not granting the Lambda function the correct IAM permissions to access DynamoDB.
• Using the wrong region or table name in the client configuration.
• Incorrectly formatting the item attributes (DynamoDB expects types like S for string, N for number).
• Not handling async calls properly, causing the function to exit before DynamoDB operations complete.

javascript

/* Wrong: Missing IAM permission or wrong region */
const clientWrong = new DynamoDBClient({ region: "wrong-region" });

/* Right: Correct region and ensure IAM role has DynamoDB access */
const clientRight = new DynamoDBClient({ region: "us-east-1" });

Quick Reference

Step	Description
1. Create Lambda	Set up a Lambda function in AWS console or CLI.
2. Add IAM Role	Attach a role with DynamoDB access permissions.
3. Install SDK	Use AWS SDK v3 in your Lambda code.
4. Initialize Client	Create DynamoDBClient with correct region.
5. Use Commands	Use PutItemCommand, GetItemCommand, etc., to interact.
6. Handle Async	Use async/await to wait for operations to finish.

Key Takeaways

Grant your Lambda function IAM permissions to access DynamoDB tables.

Use AWS SDK v3 with DynamoDBClient and command objects inside Lambda.

Always specify the correct AWS region and table name in your code.

Format DynamoDB items with attribute types like S (string) and N (number).

Use async/await to ensure DynamoDB operations complete before Lambda exits.