/aws-cloudformation-lambda

name: aws-cloudformation-lambda
description: Provides AWS CloudFormation patterns for Lambda functions, layers, API Gateway integration, event sources, cold start optimization, monitoring, logging, template validation, and deployment workflows. Use when creating Lambda functions with CloudFormation, configuring event sources, implementing cold start optimization, managing layers, integrating with API Gateway, and deploying Lambda infrastructure.
allowed-tools: Read, Write, Bash

AWS CloudFormation Lambda Functions

Overview

Create production-ready Lambda functions using CloudFormation templates with validation and deployment workflows.

When to Use

• Creating Lambda functions with CloudFormation
• Configuring event sources (S3, SQS, DynamoDB, Kinesis)
• Implementing Lambda layers and cold start optimization
• Integrating Lambda with API Gateway
• Deploying Lambda infrastructure with validation

Deployment Workflow

Always follow this deployment workflow:

1. Validate Template

aws cloudformation validate-template --template-body file://template.yaml

2. Deploy Stack

aws cloudformation deploy \
  --template-file template.yaml \
  --stack-name my-lambda-stack \
  --capabilities CAPABILITY_IAM \
  --parameter-overrides Environment=prod

3. Monitor Stack Events

aws cloudformation describe-stack-events \
  --stack-name my-lambda-stack \
  --query 'StackEvents[?ResourceStatus==`CREATE_FAILED`||ResourceStatus==`UPDATE_FAILED`]'

4. Verify Resources

aws lambda get-function --function-name my-lambda-stack-function
aws cloudformation describe-stacks --stack-name my-lambda-stack \
  --query 'Stacks[0].StackStatus'

5. Rollback on Failure

aws cloudformation delete-stack --stack-name my-lambda-stack
aws logs describe-log-groups --log-group-name-prefix "/aws/lambda/my-lambda"

Instructions

Follow these steps to create Lambda functions with CloudFormation:

1. Define Lambda Function Parameters

Specify runtime, memory, timeout, and environment variables:

Parameters:
  FunctionMemory:
    Type: Number
    Default: 256
    AllowedValues:
      - 128
      - 256
      - 512
      - 1024
      - 2048
    Description: Lambda function memory in MB

  FunctionTimeout:
    Type: Number
    Default: 30
    MinValue: 1
    MaxValue: 900
    Description: Function timeout in seconds

  Runtime:
    Type: String
    Default: nodejs20.x
    AllowedValues:
      - nodejs20.x
      - python3.11
      - java21
      - dotnet8
      - go1.x
    Description: Lambda runtime environment

2. Create Lambda Function

Define the basic function configuration:

Resources:
  LambdaFunction:
    Type: AWS::Lambda::Function
    Properties:
      FunctionName: !Sub "${AWS::StackName}-function"
      Runtime: !Ref Runtime
      Handler: index.handler
      Role: !Ref ExecutionRole
      MemorySize: !Ref FunctionMemory
      Timeout: !Ref FunctionTimeout
      Code:
        S3Bucket: !Ref CodeBucket
        S3Key: !Ref CodeKey
      Environment:
        Variables:
          LOG_LEVEL: INFO
          DATABASE_URL: !Ref DatabaseUrl
      Tags:
        - Key: Environment
          Value: !Ref Environment

3. Configure Execution Role

Apply least privilege IAM policies:

Resources:
  ExecutionRole:
    Type: AWS::IAM::Role
    Properties:
      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
      Policies:
        - PolicyName: S3ReadAccess
          PolicyDocument:
            Version: "2012-10-17"
            Statement:
              - Effect: Allow
                Action:
                  - s3:GetObject
                Resource: !Sub "${DataBucket.Arn}/*"

4. Add Event Sources

Configure triggers for Lambda invocation:

Resources:
  # S3 event source
  S3EventSource:
    Type: AWS::Lambda::EventSourceMapping
    Properties:
      EventSourceArn: !GetAtt DataBucket.Arn
      FunctionName: !Ref LambdaFunction

  # SQS event source
  SQSEventSource:
    Type: AWS::Lambda::EventSourceMapping
    Properties:
      EventSourceArn: !GetAtt Queue.Arn
      FunctionName: !Ref LambdaFunction
      BatchSize: 10
      MaximumBatchingWindowInSeconds: 5

5. Configure API Gateway Integration

Set up REST or HTTP API integration:

Resources:
  # HTTP API integration
  HttpApi:
    Type: AWS::ApiGatewayV2::Api
    Properties:
      Name: !Sub "${AWS::StackName}-api"
      ProtocolType: HTTP
      Target: !Ref LambdaFunction

  ApiIntegration:
    Type: AWS::ApiGatewayV2::Integration
    Properties:
      ApiId: !Ref HttpApi
      IntegrationType: AWS_PROXY
      IntegrationUri: !Sub "arn:aws:apigateway:${AWS::Region}:lambda:path/2015-03-31/functions/${LambdaFunction.Arn}/invocations"

6. Implement Versioning and Aliases

Create function versions and aliases:

Resources:
  LambdaVersion:
    Type: AWS::Lambda::Version
    Properties:
      FunctionName: !Ref LambdaFunction
      Description: !Sub "Version ${AWS::StackName} v1"

  LambdaAlias:
    Type: AWS::Lambda::Alias
    Properties:
      FunctionName: !Ref LambdaFunction
      FunctionVersion: !GetAtt LambdaVersion.Version
      Name: live

7. Configure Monitoring

Enable CloudWatch logging and X-Ray tracing:

Resources:
  LambdaFunction:
    Type: AWS::Lambda::Function
    Properties:
      LoggingConfig:
        LogGroup: !Ref LogGroup
      TracingConfig:
        Mode: Active

  LogGroup:
    Type: AWS::Logs::LogGroup
    Properties:
      LogGroupName: !Sub "/aws/lambda/${LambdaFunction}"
      RetentionInDays: 7

8. Set Up Dead Letter Queue

Configure DLQ for failed invocations:

Resources:
  DeadLetterQueue:
    Ty