Serverless Application Model (SAM) in AWS - Mini Project: Build & Apply

Build a Simple Serverless API with AWS SAM

📖 Scenario: You are creating a simple serverless API to handle user requests without managing servers. AWS SAM helps you define and deploy this API easily.

🎯 Goal: Build an AWS SAM template that defines a Lambda function triggered by an API Gateway HTTP GET request.

📋 What You'll Learn

Create a SAM template with AWS::Serverless::Function resource

Define a Lambda function named UserFunction

Set the runtime to python3.12

Add an API Gateway event trigger for HTTP GET on path /users

Specify the handler as app.lambda_handler

💡 Why This Matters

🌍 Real World

Serverless applications let you run code without managing servers. AWS SAM simplifies building and deploying these applications.

💼 Career

Understanding AWS SAM is essential for cloud developers and architects working with serverless architectures on AWS.

1

Create the basic SAM template structure

Create a SAM template starting with AWSTemplateFormatVersion set to '2010-09-09' and Transform set to 'AWS::Serverless-2016-10-31'. Also add an empty Resources section.

AWS

# Your code here

Hint

Start with the SAM template header and an empty Resources dictionary.

2

Add the Lambda function resource

Inside Resources, add a resource named UserFunction of type AWS::Serverless::Function. Set the Runtime to python3.12 and the Handler to app.lambda_handler.

AWS

AWSTemplateFormatVersion: '2010-09-09'
Transform: 'AWS::Serverless-2016-10-31'
Resources:
  # Add UserFunction resource here

Hint

Define the Lambda function resource with the correct runtime and handler.

3

Add API Gateway event trigger

Under UserFunction properties, add an Events section. Define an event named UserApi with Type set to Api. Set the Properties of this event to have Path as /users and Method as get.

AWS

AWSTemplateFormatVersion: '2010-09-09'
Transform: 'AWS::Serverless-2016-10-31'
Resources:
  UserFunction:
    Type: AWS::Serverless::Function
    Properties:
      Runtime: python3.12
      Handler: app.lambda_handler
      # Add Events section here

Hint

Add the API Gateway event trigger under the Lambda function properties.

4

Add function memory size and timeout

Under UserFunction properties, add MemorySize set to 128 and Timeout set to 10 seconds to optimize the function configuration.

AWS

AWSTemplateFormatVersion: '2010-09-09'
Transform: 'AWS::Serverless-2016-10-31'
Resources:
  UserFunction:
    Type: AWS::Serverless::Function
    Properties:
      Runtime: python3.12
      Handler: app.lambda_handler
      Events:
        UserApi:
          Type: Api
          Properties:
            Path: /users
            Method: get
      # Add MemorySize and Timeout here

Hint

Set memory size and timeout to control function resources and execution time.

Practice

1. What is the main purpose of AWS Serverless Application Model (SAM)?

easy

A. To simplify building and deploying serverless applications using a single template

B. To manage virtual machines in the cloud

C. To create relational databases automatically

D. To monitor network traffic in AWS

Solution

1. Step 1: Understand SAM's role

   SAM is designed to help developers define serverless functions and their triggers in one file.

2. Step 2: Compare options

   Options A, B, and C describe unrelated AWS services or functions, while D correctly describes SAM's purpose.

3. Final Answer:

   To simplify building and deploying serverless applications using a single template -> Option A

4. Quick Check:

   SAM purpose = Simplify serverless apps [OK]

Hint: SAM = single template for serverless apps [OK]

Common Mistakes:

• Confusing SAM with EC2 or database services
• Thinking SAM manages infrastructure like VMs
• Assuming SAM is for monitoring

2. Which of the following is the correct syntax to define a Lambda function in a SAM template?

easy

A. MyFunction:
Type: AWS::Serverless::Function
Properties:
Handler: index.handler
Runtime: python3.8

B. MyFunction:
Type: AWS::Lambda::Function
Properties:
Handler: index.handler
Runtime: python3.8

C. MyFunction:
Type: AWS::EC2::Instance
Properties:
Handler: index.handler
Runtime: python3.8

D. MyFunction:
Type: AWS::S3::Bucket
Properties:
Handler: index.handler
Runtime: python3.8

Solution

1. Step 1: Identify SAM Lambda function resource type

   SAM uses the resource type AWS::Serverless::Function to define Lambda functions.

2. Step 2: Check other options

   MyFunction: Type: AWS::Lambda::Function Properties: Handler: index.handler Runtime: python3.8 uses AWS::Lambda::Function which is CloudFormation but not SAM shorthand. Options C and D are unrelated resource types.

3. Final Answer:

   MyFunction with Type AWS::Serverless::Function and correct properties -> Option A

4. Quick Check:

   SAM Lambda function type = AWS::Serverless::Function [OK]

Hint: SAM Lambda uses AWS::Serverless::Function type [OK]

Common Mistakes:

• Using AWS::Lambda::Function instead of AWS::Serverless::Function
• Confusing resource types like EC2 or S3 for Lambda
• Missing required properties like Handler or Runtime

3. Given this SAM template snippet, what event triggers the Lambda function?

MyFunction:
  Type: AWS::Serverless::Function
  Properties:
    Handler: app.lambda_handler
    Runtime: python3.8
    Events:
      ApiEvent:
        Type: Api
        Properties:
          Path: /hello
          Method: get

medium

A. A scheduled timer triggers the Lambda

B. An S3 file upload triggers the Lambda

C. A DynamoDB table update triggers the Lambda

D. An HTTP GET request to /hello triggers the Lambda

Solution

1. Step 1: Identify event type in template

   The event type is Api with Path /hello and Method get, meaning an HTTP GET request triggers the function.

2. Step 2: Eliminate other event types

   S3 upload, scheduled timer, and DynamoDB update are different event types not shown here.

3. Final Answer:

   An HTTP GET request to /hello triggers the Lambda -> Option D

4. Quick Check:

   Api event with GET /hello = HTTP trigger [OK]

Hint: Api event with Method get means HTTP GET trigger [OK]

Common Mistakes:

• Confusing Api event with S3 or timer events
• Ignoring the Method and Path properties
• Assuming default triggers without checking Events

4. You wrote this SAM template but deployment fails. What is the error?

MyFunction:
  Type: AWS::Serverless::Function
  Properties:
    Handler: app.lambda_handler
    Runtime: python3.8
    Events:
      S3Event:
        Type: S3
        Properties:
          Bucket: my-bucket
          Events: s3:ObjectCreated:Put

medium

A. The Runtime python3.8 is not supported

B. The Handler property is missing

C. The Events property under S3Event should be a list, not a string

D. The Bucket name cannot be hardcoded

Solution

1. Step 1: Check S3 event syntax

   The Events property for S3 event must be a list of event types, but here it is a string.

2. Step 2: Verify other properties

   Handler is present, python3.8 is supported, and bucket names can be hardcoded in SAM templates.

3. Final Answer:

   The Events property under S3Event should be a list, not a string -> Option C

4. Quick Check:

   S3 Events property = list, not string [OK]

Hint: S3 Events must be a list, not a single string [OK]

Common Mistakes:

• Using string instead of list for S3 Events
• Removing required Handler property
• Assuming runtime version is invalid without checking

5. You want to deploy a serverless app with two Lambda functions triggered by different events: one by HTTP GET /users and another by S3 file upload to bucket 'data-bucket'. Which SAM template snippet correctly defines both functions?

hard

A. UserFunction:
Type: AWS::Serverless::Function
Properties:
Handler: user.handler
Runtime: python3.8
Events:
S3Event:
Type: S3
Properties:
Bucket: data-bucket
Events:
- s3:ObjectCreated:Put

UploadFunction:
Type: AWS::Serverless::Function
Properties:
Handler: upload.handler
Runtime: python3.8
Events:
ApiEvent:
Type: Api
Properties:
Path: /users
Method: get

B. UserFunction:
Type: AWS::Serverless::Function
Properties:
Handler: user.handler
Runtime: python3.8
Events:
ApiEvent:
Type: Api
Properties:
Path: /users
Method: get

UploadFunction:
Type: AWS::Serverless::Function
Properties:
Handler: upload.handler
Runtime: python3.8
Events:
S3Event:
Type: S3
Properties:
Bucket: data-bucket
Events:
- s3:ObjectCreated:Put

C. UserFunction:
Type: AWS::Lambda::Function
Properties:
Handler: user.handler
Runtime: python3.8
Events:
ApiEvent:
Type: Api
Properties:
Path: /users
Method: get

UploadFunction:
Type: AWS::Lambda::Function
Properties:
Handler: upload.handler
Runtime: python3.8
Events:
S3Event:
Type: S3
Properties:
Bucket: data-bucket
Events:
- s3:ObjectCreated:Put

D. UserFunction:
Type: AWS::Serverless::Function
Properties:
Handler: user.handler
Runtime: python3.8
Events:
ApiEvent:
Type: Api
Properties:
Path: /users
Method: post

UploadFunction:
Type: AWS::Serverless::Function
Properties:
Handler: upload.handler
Runtime: python3.8
Events:
S3Event:
Type: S3
Properties:
Bucket: data-bucket
Events:
- s3:ObjectCreated:Put

Solution

1. Step 1: Verify UserFunction HTTP event

   UserFunction must have Api event with Path /users and Method get. UserFunction: Type: AWS::Serverless::Function Properties: Handler: user.handler Runtime: python3.8 Events: ApiEvent: Type: Api Properties: Path: /users Method: get UploadFunction: Type: AWS::Serverless::Function Properties: Handler: upload.handler Runtime: python3.8 Events: S3Event: Type: S3 Properties: Bucket: data-bucket Events: - s3:ObjectCreated:Put matches this exactly.

2. Step 2: Verify UploadFunction S3 event

   UploadFunction must have S3 event with Bucket data-bucket and Events as a list including s3:ObjectCreated:Put. UserFunction: Type: AWS::Serverless::Function Properties: Handler: user.handler Runtime: python3.8 Events: ApiEvent: Type: Api Properties: Path: /users Method: get UploadFunction: Type: AWS::Serverless::Function Properties: Handler: upload.handler Runtime: python3.8 Events: S3Event: Type: S3 Properties: Bucket: data-bucket Events: - s3:ObjectCreated:Put correctly defines this.

3. Step 3: Check other options

   UserFunction: Type: AWS::Serverless::Function Properties: Handler: user.handler Runtime: python3.8 Events: S3Event: Type: S3 Properties: Bucket: data-bucket Events: - s3:ObjectCreated:Put UploadFunction: Type: AWS::Serverless::Function Properties: Handler: upload.handler Runtime: python3.8 Events: ApiEvent: Type: Api Properties: Path: /users Method: get swaps triggers between functions. UserFunction: Type: AWS::Lambda::Function Properties: Handler: user.handler Runtime: python3.8 Events: ApiEvent: Type: Api Properties: Path: /users Method: get UploadFunction: Type: AWS::Lambda::Function Properties: Handler: upload.handler Runtime: python3.8 Events: S3Event: Type: S3 Properties: Bucket: data-bucket Events: - s3:ObjectCreated:Put uses AWS::Lambda::Function instead of AWS::Serverless::Function. UserFunction: Type: AWS::Serverless::Function Properties: Handler: user.handler Runtime: python3.8 Events: ApiEvent: Type: Api Properties: Path: /users Method: post UploadFunction: Type: AWS::Serverless::Function Properties: Handler: upload.handler Runtime: python3.8 Events: S3Event: Type: S3 Properties: Bucket: data-bucket Events: - s3:ObjectCreated:Put uses Method post instead of get for UserFunction.

4. Final Answer:

   Correctly defines both functions with proper triggers -> Option B

5. Quick Check:

   Correct event types and methods = UserFunction: Type: AWS::Serverless::Function Properties: Handler: user.handler Runtime: python3.8 Events: ApiEvent: Type: Api Properties: Path: /users Method: get UploadFunction: Type: AWS::Serverless::Function Properties: Handler: upload.handler Runtime: python3.8 Events: S3Event: Type: S3 Properties: Bucket: data-bucket Events: - s3:ObjectCreated:Put [OK]

Hint: Match event types and methods exactly for each function [OK]

Common Mistakes:

• Swapping event triggers between functions
• Using AWS::Lambda::Function instead of AWS::Serverless::Function
• Wrong HTTP method for API event