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AWS for Backend Developers (EC2, S3, RDS, Lambda) · Lesson

Serverless Application Model (SAM)

Define, develop, and deploy serverless applications using the AWS Serverless Application Model (SAM) framework.

Serverless Application Model (SAM) is a free AWS for Backend Developers (EC2, S3, RDS, Lambda) lesson on CoddyKit — lesson 3 of 4. You can read the complete lesson below for free — then practise it hands-on in the browser with a built-in code editor and a 24/7 AI tutor. It is part of the AWS for Backend Developers (EC2, S3, RDS, Lambda) learning path, one of 4 lessons in the course, and your progress syncs across the web and the CoddyKit app.

What is AWS SAM?

Welcome to the AWS Serverless Application Model (SAM)! SAM is an open-source framework that helps you build, test, and deploy serverless applications on AWS faster and easier.

Think of it as a simplified way to define your serverless resources like Lambda functions and API Gateway endpoints.

SAM: CloudFormation's Helper

At its core, SAM is an extension of AWS CloudFormation. It provides a shorthand syntax for common serverless components.

When you deploy a SAM application, SAM transforms your simplified template into a full AWS CloudFormation template, ensuring you get all the benefits of CloudFormation's robust deployment capabilities.

SAM Template Structure

SAM applications are defined in a SAM template, typically a YAML file named template.yaml. Key sections include:

  • AWSTemplateFormatVersion: Standard CloudFormation version.
  • Transform: AWS::Serverless-2016-10-31: This line tells CloudFormation to process the template using SAM.
  • Resources: Where you define your serverless components (functions, APIs, databases).

Defining a Serverless Function

The primary resource for a Lambda function in SAM is AWS::Serverless::Function. This resource simplifies defining a Lambda function and its related configurations.

You specify properties like Handler (the function entry point), Runtime (e.g., python3.9), and CodeUri (the path to your function's code).

Integrating with API Gateway

To expose your Lambda function via an HTTP endpoint, you can directly define Events within your AWS::Serverless::Function resource.

Using the Api event type automatically provisions an Amazon API Gateway endpoint. You specify the Path and Method for your API route.

Your First SAM Template

Here's a basic template.yaml that defines a Python Lambda function triggered by an API Gateway GET request on the /hello path.

The CodeUri: hello_world/ indicates that the Lambda code is in a local directory named hello_world.

AWSTemplateFormatVersion: '2010-09-09'
Transform: AWS::Serverless-2016-10-31
Description: A simple "Hello World" SAM app.

Resources:
  HelloWorldFunction:
    Type: AWS::Serverless::Function
    Properties:
      Handler: app.lambda_handler
      Runtime: python3.9
      CodeUri: hello_world/
      MemorySize: 128
      Timeout: 30
      Events:
        HelloWorldApi:
          Type: Api
          Properties:
            Path: /hello
            Method: GET

The Lambda Function Code

This is the Python code (app.py) that resides inside the hello_world/ directory. This function will be executed when the API Gateway endpoint is invoked.

It simply returns a JSON response with a "Hello from SAM Lambda!" message.

import json

def lambda_handler(event, context):
    """
    Handles API Gateway requests and returns a simple greeting.
    """
    print("Received an event:", event) # For logging
    return {
        "statusCode": 200,
        "headers": {
            "Content-Type": "application/json"
        },
        "body": json.dumps({
            "message": "Hello from SAM Lambda!"
        }),
    }

# Example local invocation (for direct script testing)
if __name__ == "__main__":
    test_event = {
        "httpMethod": "GET",
        "path": "/hello",
        "requestContext": {"requestId": "test-id-123"},
        "headers": {"User-Agent": "test-client"}
    }
    response = lambda_handler(test_event, None)
    print("Local Response:", response)

Building Your SAM Application

Before you can deploy or even test your application locally, you need to build it. The sam build command processes your template, gathers dependencies, and prepares your code for deployment.

It creates a .aws-sam/build directory containing the processed artifacts.

sam build

Testing Locally with SAM CLI

The SAM CLI provides powerful tools for local testing, saving you time and money by avoiding repeated deployments to AWS.

  • sam local invoke: Invokes a single Lambda function locally with a given event.
  • sam local start-api: Starts a local HTTP server that emulates API Gateway, allowing you to interact with your serverless API from your browser or curl.

sam local start-api

Deploying Your Serverless App

Once your application is built and tested locally, you can deploy it to AWS using the sam deploy command.

The first time you deploy, it's recommended to use the --guided flag. This provides an interactive prompt to configure settings like stack name, AWS Region, and S3 bucket for deployment artifacts.

sam deploy --guided

SAM CLI Quick Check

Which SAM CLI command is used to test your serverless API Gateway locally, allowing you to interact with it from your browser or curl?

Recap & Next Steps

Congratulations! You've learned the fundamentals of the AWS Serverless Application Model (SAM).

  • SAM simplifies serverless development by extending CloudFormation.
  • You can define Lambda functions and API Gateway endpoints easily in a template.yaml.
  • The SAM CLI allows you to build, test locally, and deploy your serverless applications efficiently.

SAM is a powerful tool for developing modern, event-driven applications on AWS!

Frequently asked questions

Is the “Serverless Application Model (SAM)” lesson free?

Yes — the full text of “Serverless Application Model (SAM)” is free to read here on the web, and the AWS for Backend Developers (EC2, S3, RDS, Lambda) course includes 4 lessons in total. To practise it interactively (a built-in code editor and a 24/7 AI tutor) and unlock the rest of the AWS for Backend Developers (EC2, S3, RDS, Lambda) course, upgrade to CoddyKit PRO.

What will I learn in “Serverless Application Model (SAM)”?

Define, develop, and deploy serverless applications using the AWS Serverless Application Model (SAM) framework. You practise AWS for Backend Developers (EC2, S3, RDS, Lambda) with hands-on code you run directly in the browser, and a 24/7 AI tutor answers your questions as you work through the lesson.

Do I need any experience to start AWS for Backend Developers (EC2, S3, RDS, Lambda)?

No prior experience is required. AWS for Backend Developers (EC2, S3, RDS, Lambda) on CoddyKit is structured for beginners through advanced learners; this is — lesson 3 of 4, so you can start here or from the beginning and move at your own pace.

How long does the “Serverless Application Model (SAM)” lesson take?

Most CoddyKit lessons take about 5–10 minutes. Each one is bite-sized and interactive, so you make steady progress and pick up exactly where you left off across the web and the app.

Can I write and run code in this AWS for Backend Developers (EC2, S3, RDS, Lambda) lesson?

Yes. Every AWS for Backend Developers (EC2, S3, RDS, Lambda) lesson includes a built-in code editor, so you write and run real code right in your browser and get instant AI feedback — no local setup required.

All lessons in this course

  1. CodeCommit and CodeBuild Basics
  2. CodeDeploy for EC2/Lambda
  3. Serverless Application Model (SAM)
  4. Infrastructure as Code with CloudFormation
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