Lambda & Serverless

Duration: 50 min

AWS Lambda lets you run code without provisioning or managing servers. You upload code, set triggers, and Lambda automatically scales. This module covers Lambda functions, triggers, API Gateway, and the Serverless Application Model (SAM).

Lambda Basics

AWS Lambda is a serverless compute service. You write functions in Python, Node.js, Java, Go, or other languages. Lambda automatically scales from zero to thousands of concurrent executions.

You pay only for compute time consumed, measured in milliseconds. There's a generous free tier: 1 million requests and 400,000 GB-seconds per month.

Lambda Triggers

Lambda functions are triggered by events from other AWS services:

API Gateway triggers Lambda when HTTP requests arrive.

S3 triggers Lambda when objects are uploaded or deleted.

DynamoDB Streams trigger Lambda when data changes.

SNS triggers Lambda when messages are published.

CloudWatch Events trigger Lambda on a schedule (cron).

SQS triggers Lambda when messages arrive in a queue.

API Gateway

API Gateway creates REST or WebSocket APIs that trigger Lambda functions. It handles authentication, rate limiting, and request/response transformation.

Hands-On: Create Lambda Function

Create a simple Lambda function:

cat > lambda_function.py << 'EOF'
def lambda_handler(event, context):
    return {
        'statusCode': 200,
        'body': 'Hello from Lambda!'
    }
EOF

Package and deploy:

zip lambda.zip lambda_function.py

aws lambda create-function --function-name my-function \
  --runtime python3.11 --role arn:aws:iam::ACCOUNT:role/lambda-role \
  --handler lambda_function.lambda_handler --zip-file fileb://lambda.zip

Invoke the function:

aws lambda invoke --function-name my-function response.json
cat response.json

Create an API Gateway trigger:

aws apigateway create-rest-api --name my-api
aws apigateway create-resource --rest-api-id api-id --parent-id root-id \
  --path-part hello
aws apigateway put-method --rest-api-id api-id --resource-id resource-id \
  --http-method GET --authorization-type NONE

Python Boto3 Example

import boto3
import json

lambda_client = boto3.client('lambda')

# Create function
response = lambda_client.create_function(
    FunctionName='my-function',
    Runtime='python3.11',
    Role='arn:aws:iam::ACCOUNT:role/lambda-role',
    Handler='lambda_function.lambda_handler',
    Code={'ZipFile': b'function code here'}
)

# Invoke function
response = lambda_client.invoke(
    FunctionName='my-function',
    InvocationType='RequestResponse',
    Payload=json.dumps({'key': 'value'})
)

print(json.loads(response['Payload'].read()))

# Update function code
lambda_client.update_function_code(
    FunctionName='my-function',
    ZipFile=b'new function code'
)

Serverless Application Model (SAM)

SAM is a framework for building serverless applications. Define your Lambda functions, API Gateway, and other resources in a YAML template:

AWSTemplateFormatVersion: '2010-09-09'
Transform: AWS::Serverless-2016-10-31

Resources:
  MyFunction:
    Type: AWS::Serverless::Function
    Properties:
      FunctionName: my-function
      Runtime: python3.11
      Handler: lambda_function.lambda_handler
      CodeUri: .
      Events:
        ApiEvent:
          Type: Api
          Properties:
            RestApiId: !Ref MyApi
            Path: /hello
            Method: GET

  MyApi:
    Type: AWS::Serverless::Api
    Properties:
      StageName: prod

Deploy with SAM:

sam build
sam deploy --guided

Terraform Example

resource "aws_lambda_function" "my_function" {
  filename      = "lambda.zip"
  function_name = "my-function"
  role          = aws_iam_role.lambda_role.arn
  handler       = "lambda_function.lambda_handler"
  runtime       = "python3.11"
}

resource "aws_apigatewayv2_api" "my_api" {
  name          = "my-api"
  protocol_type = "HTTP"
}

resource "aws_apigatewayv2_integration" "lambda_integration" {
  api_id           = aws_apigatewayv2_api.my_api.id
  integration_type = "AWS_PROXY"
  integration_method = "POST"
  payload_format_version = "2.0"
  target           = aws_lambda_function.my_function.arn
}

Quiz 1

Quiz 2

Quiz 3

Quiz 4

Quiz 5