Lambda trigger on stream events in DynamoDB - Mini Project: Build & Apply

Lambda Trigger on DynamoDB Stream Events

📖 Scenario: You are building a simple inventory system using DynamoDB. You want to automatically process changes to the inventory items whenever they are added or updated. To do this, you will set up a Lambda function that triggers on DynamoDB stream events.

🎯 Goal: Create a DynamoDB table with a stream enabled, configure a Lambda function to trigger on the stream events, and write the Lambda function code to process the incoming stream records.

📋 What You'll Learn

Create a DynamoDB table named Inventory with a primary key ItemId (string).

Enable a stream on the Inventory table with NEW_IMAGE view type.

Create a Lambda function named ProcessInventoryStream that triggers on the DynamoDB stream events.

Write Lambda function code to iterate over the stream records and log the ItemId and Quantity of each new image.

💡 Why This Matters

🌍 Real World

Automatically reacting to database changes is common in real-time applications like inventory management, notifications, and analytics.

💼 Career

Understanding how to connect DynamoDB streams with Lambda functions is a key skill for AWS developers and cloud engineers working on serverless architectures.

1

Create DynamoDB Table with Stream Enabled

Create a DynamoDB table named Inventory with a primary key called ItemId of type string. Enable the stream on this table with the view type set to NEW_IMAGE.

DynamoDB

# Your code here to create DynamoDB table Inventory with ItemId as string primary key and stream enabled with NEW_IMAGE

Need a hint?

Use the AWS CLI aws dynamodb create-table command with the --stream-specification option.

2

Configure Lambda Trigger on DynamoDB Stream

Create a Lambda function named ProcessInventoryStream and configure it to trigger on the DynamoDB stream of the Inventory table. Use the stream ARN from the table description as the event source.

DynamoDB

aws dynamodb create-table \
    --table-name Inventory \
    --attribute-definitions AttributeName=ItemId,AttributeType=S \
    --key-schema AttributeName=ItemId,KeyType=HASH \
    --provisioned-throughput ReadCapacityUnits=5,WriteCapacityUnits=5 \
    --stream-specification StreamEnabled=true,StreamViewType=NEW_IMAGE

# Your code here to create Lambda function ProcessInventoryStream and add DynamoDB stream trigger

Need a hint?

Use aws lambda create-function to create the Lambda and aws lambda create-event-source-mapping to connect the stream.

3

Write Lambda Function Code to Process Stream Records

Write the Lambda function code in Python that iterates over the Records in the event. For each record, extract the ItemId and Quantity from the NewImage and log them using print.

DynamoDB

def lambda_handler(event, context):
    # Your code here to process stream records and print ItemId and Quantity

Need a hint?

Use event['Records'] to loop through records and access NewImage data.

4

Deploy Lambda Function Code and Finalize Setup

Package the Lambda function code into a zip file named function.zip and update the Lambda function ProcessInventoryStream with this code. Ensure the Lambda function has permission to read from the DynamoDB stream.

DynamoDB

# Your code here to update Lambda function code with function.zip and add necessary permissions

Need a hint?

Use aws lambda update-function-code to deploy and aws lambda add-permission to grant stream invoke rights.