Mastering Serverless with AWS SAM

AWS Lambda is a serverless compute service that lets you run code without provisioning or managing servers. AWS SAM (Serverless Application Model) is an open-source framework that makes building and deploying serverless applications easier. In this guide, we will walk through setting up an AWS Lambda function using Node.js and AWS SAM.

Step 1: Create a New AWS SAM Application

To begin, open a terminal and run:

sam init 

Select the following options when prompted:

Template source: AWS Quick Start Templates

Runtime: nodejs22.x (or latest available)

Package type: Zip

Project name: aws-sam-node-lambda

Once completed, navigate to the project directory:

cd aws-sam-node-lambda 

Step 2: Understanding the Project Structure

Your SAM project contains several files and folders:

aws-sam-node-lambda/ ├── functions │ ├──hello-world/ │ ├── app.js # Lambda function code │ ├── package.json # Node.js dependencies │ ├── tests/ # Unit tests ├── template.yaml # AWS SAM template defining resources 

The template.yaml file is crucial as it defines your AWS resources.

Step 3: Writing the Lambda Function

Modify hello-world/app.js to:

exports.lambdaHandler = async (event, context) => { return { statusCode: 200, body: JSON.stringify({ message: "Hello from AWS Lambda with Node.js and SAM!" }) }; }; 

Step 4: Build and Test Locally

Before deploying, build the function:

sam build 

To invoke it locally:

sam local invoke HelloWorldFunction 

Expected output:

{ "statusCode": 200, "body": "{\"message\":\"Hello from AWS Lambda with Node.js and SAM!\"}" }