Lambda with DynamoDB Streams in AWS - Mini Project: Build & Apply

Lambda with DynamoDB Streams

📖 Scenario: You are building a simple serverless application where changes in a DynamoDB table trigger a Lambda function. This Lambda function processes the stream records from DynamoDB to react to data changes.

🎯 Goal: Create an AWS Lambda function triggered by DynamoDB Streams. The Lambda function will receive stream events and log the event details.

📋 What You'll Learn

Create a DynamoDB table with streams enabled

Create a Lambda function with the correct IAM role

Configure the Lambda function to be triggered by the DynamoDB stream

Write Lambda code to process and log stream events

💡 Why This Matters

🌍 Real World

Many serverless applications use DynamoDB Streams to react to data changes in real time, such as updating caches, sending notifications, or triggering workflows.

💼 Career

Understanding how to connect DynamoDB Streams with Lambda is a common task for cloud engineers and developers working with AWS serverless architectures.

1

Create DynamoDB Table with Streams Enabled

Create a DynamoDB table named Orders with a primary key OrderId of type string. Enable DynamoDB Streams with NEW_IMAGE view type.

AWS

# Create a DynamoDB table resource named 'Orders' with 'OrderId' as the partition key and streams enabled
# Your code here

Need a hint?

Use AWS CloudFormation syntax to define a DynamoDB table resource. Remember to enable streams with StreamSpecification.

2

Create IAM Role for Lambda Function

Create an IAM role named LambdaExecutionRole with a trust policy for Lambda service and attach the managed policy AWSLambdaBasicExecutionRole. This role will allow Lambda to write logs.

AWS

Resources:
  OrdersTable:
    Type: AWS::DynamoDB::Table
    Properties:
      TableName: Orders
      AttributeDefinitions:
        - AttributeName: OrderId
          AttributeType: S
      KeySchema:
        - AttributeName: OrderId
          KeyType: HASH
      BillingMode: PAY_PER_REQUEST
      StreamSpecification:
        StreamViewType: NEW_IMAGE

# Create IAM role 'LambdaExecutionRole' with trust policy for Lambda and attach AWSLambdaBasicExecutionRole
# Your code here

Need a hint?

Define an IAM role resource with a trust policy for Lambda and attach the AWS managed policy for basic Lambda execution.

3

Create Lambda Function with DynamoDB Stream Trigger

Create a Lambda function named ProcessOrderStream using runtime python3.12. Assign the role LambdaExecutionRole. Configure the function to be triggered by the DynamoDB stream of the Orders table with batch size 5 and starting position TRIM_HORIZON.

AWS

Resources:
  OrdersTable:
    Type: AWS::DynamoDB::Table
    Properties:
      TableName: Orders
      AttributeDefinitions:
        - AttributeName: OrderId
          AttributeType: S
      KeySchema:
        - AttributeName: OrderId
          KeyType: HASH
      BillingMode: PAY_PER_REQUEST
      StreamSpecification:
        StreamViewType: NEW_IMAGE

  LambdaExecutionRole:
    Type: AWS::IAM::Role
    Properties:
      RoleName: LambdaExecutionRole
      AssumeRolePolicyDocument:
        Version: '2012-10-17'
        Statement:
          - Effect: Allow
            Principal:
              Service: lambda.amazonaws.com
            Action: sts:AssumeRole
      ManagedPolicyArns:
        - arn:aws:iam::aws:policy/service-role/AWSLambdaBasicExecutionRole

# Create Lambda function 'ProcessOrderStream' with runtime 'python3.12' and role 'LambdaExecutionRole'
# Configure event source mapping for DynamoDB stream from 'Orders' table
# Your code here

Need a hint?

Define a Lambda function resource with inline Python code. Then create an event source mapping resource to connect the DynamoDB stream to the Lambda function.

4

Add Permissions for Lambda to Read DynamoDB Stream

Add an IAM policy named LambdaDynamoDBStreamPolicy to the LambdaExecutionRole that allows dynamodb:DescribeStream, dynamodb:GetRecords, dynamodb:GetShardIterator, and dynamodb:ListStreams actions on the DynamoDB stream ARN of the Orders table.

AWS

Resources:
  OrdersTable:
    Type: AWS::DynamoDB::Table
    Properties:
      TableName: Orders
      AttributeDefinitions:
        - AttributeName: OrderId
          AttributeType: S
      KeySchema:
        - AttributeName: OrderId
          KeyType: HASH
      BillingMode: PAY_PER_REQUEST
      StreamSpecification:
        StreamViewType: NEW_IMAGE

  LambdaExecutionRole:
    Type: AWS::IAM::Role
    Properties:
      RoleName: LambdaExecutionRole
      AssumeRolePolicyDocument:
        Version: '2012-10-17'
        Statement:
          - Effect: Allow
            Principal:
              Service: lambda.amazonaws.com
            Action: sts:AssumeRole
      ManagedPolicyArns:
        - arn:aws:iam::aws:policy/service-role/AWSLambdaBasicExecutionRole

  ProcessOrderStream:
    Type: AWS::Lambda::Function
    Properties:
      FunctionName: ProcessOrderStream
      Runtime: python3.12
      Role: !GetAtt LambdaExecutionRole.Arn
      Handler: index.lambda_handler
      Code:
        ZipFile: |
          def lambda_handler(event, context):
              for record in event['Records']:
                  print('Stream record:', record)

  OrderStreamEventSourceMapping:
    Type: AWS::Lambda::EventSourceMapping
    Properties:
      EventSourceArn: !GetAtt OrdersTable.StreamArn
      FunctionName: !Ref ProcessOrderStream
      StartingPosition: TRIM_HORIZON
      BatchSize: 5

# Add IAM policy 'LambdaDynamoDBStreamPolicy' to 'LambdaExecutionRole' allowing DynamoDB stream read actions
# Your code here

Need a hint?

Add an inline policy to the Lambda execution role allowing it to read from the DynamoDB stream ARN.