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Serverless Backend with AWS Lambda & API Gateway · Lesson

Defining Serverless Resources

Write SAM templates to define Lambda functions, API Gateway endpoints, DynamoDB tables, and other serverless components.

Defining Serverless Resources is a free Serverless Backend with AWS Lambda & API Gateway lesson on CoddyKit — lesson 2 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 Serverless Backend with AWS Lambda & API Gateway learning path, one of 4 lessons in the course, and your progress syncs across the web and the CoddyKit app.

What are SAM Templates?

AWS Serverless Application Model (SAM) templates are a powerful way to define your serverless applications using Infrastructure as Code (IaC).

Instead of manually configuring resources in the AWS console, you describe them in a YAML or JSON file. This makes your deployments repeatable, version-controlled, and easier to manage.

Anatomy of a SAM Template

A SAM template has a clear structure. The most important parts are:

  • AWSTemplateFormatVersion: Specifies the template format version.
  • Transform: Always AWS::Serverless-2016-10-31 for SAM.
  • Description: A brief description of your application.
  • Resources: Where you define all your AWS components.
AWSTemplateFormatVersion: '2010-09-09'
Transform: AWS::Serverless-2016-10-31
Description: My First SAM App

Resources:
  # Your serverless resources go here

Defining a Serverless Function

The core of many serverless applications is the AWS Lambda function. In SAM, you declare a Lambda using the AWS::Serverless::Function resource type.

You need to specify its handler, runtime, and where its code is located.

Resources:
  MyLambdaFunction:
    Type: AWS::Serverless::Function
    Properties:
      Handler: app.lambda_handler
      Runtime: python3.9
      CodeUri: s3://my-bucket/my-app.zip
      MemorySize: 128
      Timeout: 30

Key Lambda Properties

Let's break down some common AWS::Serverless::Function properties:

  • Handler: The entry point in your code (e.g., filename.function_name).
  • Runtime: The programming language runtime (e.g., python3.9, nodejs18.x).
  • CodeUri: Path to your function's deployment package (local or S3).
  • MemorySize: RAM allocated to the function (MB).
  • Timeout: Max execution time (seconds).

API Gateway as an Event Source

To make your Lambda function accessible via an HTTP endpoint, you integrate it with Amazon API Gateway. In SAM, you do this by adding an Events property to your function.

The HttpApi type is often preferred for its simplicity and cost-effectiveness.

Resources:
  MyApiFunction:
    Type: AWS::Serverless::Function
    Properties:
      Handler: app.lambda_handler
      Runtime: python3.9
      CodeUri: s3://my-bucket/api-app.zip
      Events:
        MyApiEvent:
          Type: HttpApi
          Properties:
            Path: /hello
            Method: GET

Defining a DynamoDB Table

For data persistence, you can define a DynamoDB table directly in your SAM template. SAM provides a convenient AWS::Serverless::SimpleTable resource type.

This creates a basic DynamoDB table with a primary key. For more advanced configurations, you can use AWS::DynamoDB::Table.

Resources:
  MyDataTable:
    Type: AWS::Serverless::SimpleTable
    Properties:
      PrimaryKey:
        Name: id
        Type: String
      ProvisionedThroughput:
        ReadCapacityUnits: 1
        WriteCapacityUnits: 1

IAM Permissions for Resources

Your Lambda functions often need permission to interact with other AWS services, like DynamoDB. You grant these permissions using IAM (Identity and Access Management) policies.

SAM allows you to attach policies directly to your Lambda function's execution role using the Policies property.

Resources:
  MyLambdaWithDbAccess:
    Type: AWS::Serverless::Function
    Properties:
      Handler: app.lambda_handler
      Runtime: python3.9
      CodeUri: s3://my-bucket/db-app.zip
      Policies:
        - DynamoDBReadWriteAccess:
            TableName: !Ref MyDataTable # Grants access to MyDataTable
      Events:
        MyApiEvent:
          Type: HttpApi
          Properties:
            Path: /items
            Method: GET
  MyDataTable:
    Type: AWS::Serverless::SimpleTable
    Properties:
      PrimaryKey:
        Name: id
        Type: String

Exporting Important Values

After deploying your serverless application, you often need to know the endpoint URL of your API or the name of your DynamoDB table.

The Outputs section in your SAM template allows you to export these values, making them easily accessible after deployment.

Outputs:
  ApiUrl:
    Description: "API Gateway endpoint URL for Prod stage for Hello World function"
    Value: !Sub "https://${ServerlessHttpApi}.execute-api.${AWS::Region}.amazonaws.com/hello"

A Full Serverless Template

Here's a more complete SAM template that defines an HTTP API endpoint, a Lambda function to handle requests, and a DynamoDB table for data storage.

Notice how different resource types are declared and linked together.

AWSTemplateFormatVersion: '2010-09-09'
Transform: AWS::Serverless-2016-10-31
Description: A complete serverless API with Lambda and DynamoDB

Resources:
  MyApiFunction:
    Type: AWS::Serverless::Function
    Properties:
      Handler: app.lambda_handler
      Runtime: python3.9
      CodeUri: s3://my-bucket/full-app.zip
      Policies:
        - DynamoDBReadWriteAccess:
            TableName: !Ref MyItemsTable
      Events:
        MyApiEvent:
          Type: HttpApi
          Properties:
            Path: /items
            Method: GET

  MyItemsTable:
    Type: AWS::Serverless::SimpleTable
    Properties:
      PrimaryKey:
        Name: itemId
        Type: String

Outputs:
  ApiEndpoint:
    Description: "API Gateway endpoint URL"
    Value: !Sub "https://${ServerlessHttpApi}.execute-api.${AWS::Region}.amazonaws.com/items"

SAM Template Check

Which of the following are valid top-level sections in a SAM template?

Recap: Defining Serverless Resources

In this lesson, you learned how to define various serverless resources within a SAM template. We covered:

  • The basic structure of a SAM template.
  • Declaring AWS::Serverless::Function for Lambda.
  • Integrating Lambda with API Gateway using Events.
  • Defining AWS::Serverless::SimpleTable for DynamoDB.
  • Granting permissions with IAM Policies.
  • Using the Outputs section to export values.

Next, we'll learn how to deploy these templates to AWS!

Frequently asked questions

Is the “Defining Serverless Resources” lesson free?

Yes — the full text of “Defining Serverless Resources” is free to read here on the web, and the Serverless Backend with AWS Lambda & API Gateway 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 Serverless Backend with AWS Lambda & API Gateway course, upgrade to CoddyKit PRO.

What will I learn in “Defining Serverless Resources”?

Write SAM templates to define Lambda functions, API Gateway endpoints, DynamoDB tables, and other serverless components. You practise Serverless Backend with AWS Lambda & API Gateway 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 Serverless Backend with AWS Lambda & API Gateway?

No prior experience is required. Serverless Backend with AWS Lambda & API Gateway on CoddyKit is structured for beginners through advanced learners; this is — lesson 2 of 4, so you can start here or from the beginning and move at your own pace.

How long does the “Defining Serverless Resources” 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 Serverless Backend with AWS Lambda & API Gateway lesson?

Yes. Every Serverless Backend with AWS Lambda & API Gateway 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. Introduction to AWS SAM
  2. Defining Serverless Resources
  3. Deploying SAM Applications
  4. Local Testing and Debugging with SAM CLI
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