Serverless Application Model (SAM) in AWS - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is AWS Serverless Application Model (SAM)?

AWS SAM is a framework that helps you build and deploy serverless applications easily using simple templates.

beginner

Which file format does SAM use to define serverless applications?

SAM uses a YAML or JSON template file to define resources like functions, APIs, and databases.

intermediate

How does SAM simplify deploying AWS Lambda functions?

SAM lets you define Lambda functions and their triggers in one template, then deploys them with a single command.

intermediate

What command do you use to locally test a SAM application?

You use 'sam local invoke' to run Lambda functions locally and 'sam local start-api' to test APIs on your machine.

advanced

Why is SAM considered a best practice for serverless development?

SAM provides a clear structure, easy deployment, local testing, and integrates well with AWS services, making serverless development faster and safer.

What does AWS SAM primarily help you manage?

A Serverless applications

B Virtual machines

C Database schemas

D Network firewalls

AWS SAM is designed to manage serverless applications like Lambda functions and APIs.

Which file extension is commonly used for SAM templates?

A .yaml

B .exe

C .html

D .docx

SAM templates are usually written in YAML format with the .yaml extension.

Which command lets you deploy a SAM application to AWS?

A sam local invoke

B sam build

C sam delete

D sam deploy

'sam deploy' uploads your application to AWS and creates the resources.

What is the purpose of 'sam local start-api'?

A To build Lambda functions

B To test API Gateway locally

C To delete APIs

D To deploy APIs to AWS

'sam local start-api' runs your API Gateway locally for testing.

Which AWS service does SAM mainly work with?

A Amazon EC2

B Amazon RDS

C AWS Lambda

D AWS S3

SAM is focused on managing AWS Lambda functions and related serverless resources.

Explain what AWS Serverless Application Model (SAM) is and how it helps developers.

Think about how SAM makes serverless apps easier to create and manage.

Describe the process of testing and deploying a serverless application using SAM.

Consider how you test locally before sending your app to AWS.

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