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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.

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.

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.

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).

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.

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.

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.

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.

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.

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!