Lambda with API Gateway pattern in AWS - Mini Project: Build & Apply

Lambda with API Gateway pattern

📖 Scenario: You are building a simple serverless API using AWS Lambda and API Gateway. This API will respond to HTTP GET requests with a fixed message. This is a common pattern to create scalable and cost-effective web services without managing servers.

🎯 Goal: Create an AWS Lambda function and configure an API Gateway REST API to trigger this Lambda on HTTP GET requests. The Lambda should return a JSON response with a greeting message.

📋 What You'll Learn

Create a Lambda function named MyLambdaFunction with a basic handler.

Create an API Gateway REST API named MyApi.

Create a resource /greet under the API.

Create a GET method on the /greet resource that triggers the Lambda function.

Deploy the API to a stage named prod.

💡 Why This Matters

🌍 Real World

This pattern is widely used to build serverless web APIs that scale automatically and reduce operational overhead.

💼 Career

Understanding how to connect Lambda with API Gateway is essential for cloud developers and architects working with AWS serverless technologies.

1

Create the AWS Lambda function

Write the AWS CloudFormation YAML code to create a Lambda function named MyLambdaFunction with runtime python3.12, handler index.handler, and a basic inline code that returns a JSON greeting message.

AWS

# Write the AWS::Lambda::Function resource for MyLambdaFunction
# Your code here

Need a hint?

Use AWS::Lambda::Function resource with Runtime set to python3.12 and inline ZipFile code for the handler.

2

Create the API Gateway REST API and resource

Add AWS CloudFormation YAML code to create an API Gateway REST API named MyApi and a resource /greet under the root resource.

AWS

Resources:
  MyLambdaFunction:
    Type: AWS::Lambda::Function
    Properties:
      FunctionName: MyLambdaFunction
      Runtime: python3.12
      Handler: index.handler
      Role: arn:aws:iam::123456789012:role/lambda-execution-role
      Code:
        ZipFile: |
          def handler(event, context):
              return {
                  'statusCode': 200,
                  'headers': {'Content-Type': 'application/json'},
                  'body': '{"message": "Hello from Lambda!"}'
              }

# Add AWS::ApiGateway::RestApi and AWS::ApiGateway::Resource for /greet
# Your code here

Need a hint?

Create AWS::ApiGateway::RestApi for the API and AWS::ApiGateway::Resource for the /greet path.

3

Create the GET method on /greet to trigger Lambda

Add AWS CloudFormation YAML code to create a GET method on the /greet resource that integrates with the Lambda function MyLambdaFunction. Use AWS_PROXY integration type.

AWS

Resources:
  MyLambdaFunction:
    Type: AWS::Lambda::Function
    Properties:
      FunctionName: MyLambdaFunction
      Runtime: python3.12
      Handler: index.handler
      Role: arn:aws:iam::123456789012:role/lambda-execution-role
      Code:
        ZipFile: |
          def handler(event, context):
              return {
                  'statusCode': 200,
                  'headers': {'Content-Type': 'application/json'},
                  'body': '{"message": "Hello from Lambda!"}'
              }
  MyApi:
    Type: AWS::ApiGateway::RestApi
    Properties:
      Name: MyApi
  GreetResource:
    Type: AWS::ApiGateway::Resource
    Properties:
      RestApiId: !Ref MyApi
      ParentId: !GetAtt [MyApi, RootResourceId]
      PathPart: greet

# Add AWS::ApiGateway::Method for GET on /greet with Lambda integration
# Your code here

Need a hint?

Create AWS::ApiGateway::Method with HttpMethod: GET and AWS_PROXY integration to the Lambda function.

4

Deploy the API Gateway to a stage

Add AWS CloudFormation YAML code to create a deployment of the API Gateway MyApi and a stage named prod.

AWS

Resources:
  MyLambdaFunction:
    Type: AWS::Lambda::Function
    Properties:
      FunctionName: MyLambdaFunction
      Runtime: python3.12
      Handler: index.handler
      Role: arn:aws:iam::123456789012:role/lambda-execution-role
      Code:
        ZipFile: |
          def handler(event, context):
              return {
                  'statusCode': 200,
                  'headers': {'Content-Type': 'application/json'},
                  'body': '{"message": "Hello from Lambda!"}'
              }
  MyApi:
    Type: AWS::ApiGateway::RestApi
    Properties:
      Name: MyApi
  GreetResource:
    Type: AWS::ApiGateway::Resource
    Properties:
      RestApiId: !Ref MyApi
      ParentId: !GetAtt [MyApi, RootResourceId]
      PathPart: greet
  GreetGetMethod:
    Type: AWS::ApiGateway::Method
    Properties:
      RestApiId: !Ref MyApi
      ResourceId: !Ref GreetResource
      HttpMethod: GET
      AuthorizationType: NONE
      Integration:
        Type: AWS_PROXY
        IntegrationHttpMethod: POST
        Uri: !Sub arn:aws:apigateway:${AWS::Region}:lambda:path/2015-03-31/functions/${MyLambdaFunction.Arn}/invocations

# Add AWS::ApiGateway::Deployment and AWS::ApiGateway::Stage for prod
# Your code here

Need a hint?

Create AWS::ApiGateway::Deployment with DependsOn the GET method and set StageName to prod.