AWS SAM for Serverless Workloads

Deploying a Lambda Function with SAM

Let's walk through deploying a simple Lambda using AWS SAM.

Step 1: Initialize the Project

sam init

This sets up a project with:

• template.yaml: defines your infrastructure;
• hello_world/: contains your Lambda function code.

Step 2: Create the Lambda Function

Inside hello_world/app.py, define the function:

def lambda_handler(event, context):
    return {
        "statusCode": 200,
        "body": "Hello from Lambda!"
    }

Step 3: Define Infrastructure in template.yaml

Resources:
  HelloWorldFunction:
    Type: AWS::Serverless::Function
    Properties:
      CodeUri: hello_world/
      Handler: app.lambda_handler
      Runtime: python3.9

• CodeUri: Points to the function code;
• Handler: Specifies which file and function to run;
• Runtime: Defines the language runtime.

Step 4: Build the Project

sam build

This packages the application and prepares it for deployment.

Step 5: Deploy the Lambda

sam deploy --guided

The --guided flag walks you through:

• Stack Name – e.g., HelloWorldStack;
• AWS Region – e.g., us-east-1;
• Confirm changes before deploy? – Yes;
• Allow SAM CLI IAM role creation? – Yes;
• Preserve the state? – No;
• Save arguments to a samconfig.toml file? – Yes.

Once confirmed, SAM deploys:

• The Lambda function;
• The IAM role;
• API Gateway endpoint;
• Other associated resources.

Deployment Output

During deployment, you'll see updates:

• IAM Role Created;
• REST API Created;
• Lambda Permission Created;
• Gateway Deployment Created.

Deployment finishes successfully in a few minutes.

Recap

With infrastructure as code:

• You can consistently reproduce environments across regions or stages;
• You eliminate manual provisioning;
• You version and track infrastructure like application code.

That's the power of infrastructure as code!