MODULE 11 - Serverless: AWS Lambda

Overview

This module introduces serverless with AWS Lambda. It's a different paradigm where you have no servers to manage - you just write code that runs on demand.

Summative Assessment

This module includes Assessment 3 (25%) covering Lambda and validation.

LocalStack Supports Lambda!

Good news: LocalStack emulates Lambda well. You will be able to truly practice this module!

Learning Objectives

• Understand the serverless paradigm
• Compare Lambda vs virtual machines
• Create and deploy Lambda functions
• Configure minimal IAM permissions
• Analyze CloudWatch logs
• Test and validate functions

Weekly Content

1. Serverless vs VM

┌─────────────────────────────────────────────────────────────┐
│                  SERVERLESS vs VM                            │
├─────────────────────────────────────────────────────────────┤
│                                                              │
│   EC2 (VM)                         LAMBDA (Serverless)      │
│   ────────                         ────────────────────     │
│                                                              │
│   ┌─────────────────┐              ┌─────────────────┐      │
│   │    Instance     │              │    Function     │      │
│   │    (24/7)       │              │   (on demand)   │      │
│   │                 │              │                 │      │
│   │  OS + Runtime   │              │   Code only     │      │
│   │  + Application  │              │                 │      │
│   │                 │              │   Triggered by  │      │
│   │  Always UP      │              │   event         │      │
│   └─────────────────┘              └─────────────────┘      │
│                                                              │
│   You manage:                     You manage:               │
│   • OS                            • Code                    │
│   • Patching                      • Configuration           │
│   • Scaling                                                 │
│   • Availability                  AWS manages the rest!     │
│                                                              │
│   Billing:                        Billing:                  │
│   • Per hour                      • Per execution           │
│   • Even if idle                  • $0 if no execution      │
│                                                              │
└─────────────────────────────────────────────────────────────┘

2. Anatomy of a Lambda Function

# Python Example

def handler(event, context):
    """
    Handler = Entry point of the function
    
    event   = Input data (JSON)
    context = Runtime info (remaining timeout, memory...)
    """
    
    # Your logic here
    name = event.get('name', 'World')
    message = f"Hello, {name}!"
    
    # Return (format depends on the trigger)
    return {
        'statusCode': 200,
        'body': message
    }

3. Triggers

Trigger	Description	Example
API Gateway	HTTP Request	REST API
S3	File upload	Image processing
DynamoDB	Data change	Sync, notification
SQS	Queue message	Async processing
CloudWatch Events	Scheduling	Cron job
SNS	Notification	Fan-out

4. Lambda Limits

Limit	Value	Notes
Max timeout	15 minutes	Per execution
Memory	128 MB - 10 GB	Proportional CPU
Package	50 MB (zip) / 250 MB (unzipped)	Code + dependencies
Concurrency	1000 (default)	Per account/region
/tmp storage	512 MB - 10 GB	Temporary

Practical Lab with LocalStack

Create a Lambda Function

# 1. Create the function file
cat > lambda_function.py << 'EOF'
def handler(event, context):
    name = event.get('name', 'World')
    return {
        'statusCode': 200,
        'body': f'Hello, {name}!'
    }
EOF

# 2. Zip it
zip function.zip lambda_function.py

# 3. Create the function on LocalStack
awslocal lambda create-function \
    --function-name hello-function \
    --runtime python3.9 \
    --handler lambda_function.handler \
    --zip-file fileb://function.zip \
    --role arn:aws:iam::000000000000:role/lambda-role

# 4. Invoke the function
awslocal lambda invoke \
    --function-name hello-function \
    --payload '{"name": "AWS Student"}' \
    output.txt

# 5. View the result
cat output.txt

Test with API Gateway (LocalStack)

# Create a REST API
awslocal apigateway create-rest-api \
    --name 'Hello API'

# List the APIs
awslocal apigateway get-rest-apis

Assessment 3 (25%)

Format

• Practical Lab LocalStack (60%)
• Theoretical questions (40%)

Covered Content

• Creation of Lambda functions
• Invocation and tests
• Log reading
• Serverless use cases
• Comparison with EC2

Deliverable

Documented Lambda Function + tests:

• Commented source code
• Invocation screenshots
• Log analysis
• Improvement proposals

Navigation

1. Lambda Concepts
2. Function Creation
3. Validation Quiz - 30 questions to validate your knowledge
4. Lab: Lambda

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Next week: MODULE 12 - Lambda Troubleshooting