Building Serverless Applications on AWS: A Comprehensive Guide

n today’s rapidly evolving tech landscape, serverless architecture has become a game-changer for developers. It allows them to focus on writing code without worrying about managing the underlying infrastructure.

In this article, we’ll share our insights and guide you through the end-to-end process of building serverless applications using AWS Lambda and the Serverless Framework. By the end, you’ll clearly understand how to set up, write, and deploy a serverless application, along with practical insights on optimizing it for the cloud.

What You’ll Need to Get Started

Before diving into serverless development, ensure you have the following:

• An AWS account (a free-tier account is sufficient for testing and development).
• A development environment (Linux, macOS, or Windows with support for Node.js LTS or higher).
• Serverless Framework installed on your system.

Why Serverless?

Although it’s called “serverless,” servers are still involved under the hood – AWS handles the infrastructure for you. Serverless architecture abstracts the server management and allows developers to focus purely on building features.

Why is serverless architecture popular?

• Automatic scaling: AWS Lambda functions scale automatically, adjusting to the number of incoming requests.
• Cost efficiency: You only pay for the compute time when your code runsis running, which is especially useful for infrequent workloads.
• Event-driven workflows: AWS services like S3, DynamoDB, and API Gateway can trigger Lambda functions based on real-time events, making it ideal for building responsive microservices.

While serverless has numerous advantages, there are also some drawbacks:

• Cold starts: Functions can experience slow start times if not invoked in a while.
• Limited control over the environment: You don’t have direct access to the underlying server infrastructure, which limits fine-grained control.

Setting Up the Development Environment

Let’s get your environment ready for serverless development on AWS.

Step 1: Install NVM (Node Version Manager)

First, you need Node.js, and NVM makes it easy to manage multiple Node versions. Install NVM using the installation guide 

Reload your shell profile:

source ~/.bashrc

Now, install the latest LTS version of Node.js:

nvm install --lts

Verify the installation by running:

node -v

Step 2: Set Up AWS Credentials

You need to configure your AWS credentials to interact with AWS services like Lambda and S3. You can create your access and secret keys if you don’t already have them in the AWS IAM Console.

Once you have your credentials, set them in your environment:

export AWS_ACCESS_KEY_ID=<your_access_key>

export AWS_SECRET_ACCESS_KEY=<your_secret_key>

This will allow the Serverless Framework to interact with your AWS account.

Step 3: Install the Serverless Framework

Next, install the Serverless Framework globally:

npm install -g serverless

Verify the installation:

serverless --version

Step 4: Create a New Serverless Project

To create your first serverless project, use the following instructions

Understanding the Project Structure

Your project structure should look like this:

├── handler.js       # Entry point for your Lambda functions

├── serverless.yml   # Core configuration file for the Serverless Framework

├── package.json     # Node.js dependencies

├── lib/             # (Optional) Folder for internal libraries or helpers

└── node_modules/    # External Node.js modules

Here’s a brief explanation of the most important files:

• handler.js: This file contains your Lambda function logic. It acts as the entry point when your function is triggered by events (e.g., HTTP requests or S3 uploads).
• serverless.yml: This is the heart of your serverless configuration. It defines your service, AWS provider details, resources (like security roles), and events that trigger your Lambda functions.
• package.json: Your project’s Node.js dependencies.

Writing the serverless.yml Configuration

Let’s configure the serverless.yml file to manage your Lambda function, resources, and event triggers.

service: my-service # Name of your service
provider:
name: aws
runtime: nodejs20.x # Use Node.js LTS runtime
region: ${opt:region, 'us-west-2'} # Default region (can be overridden)
stage: ${opt:stage, 'dev'} # Default stage (can be overridden)
memorySize: 512 # Default memory size
timeout: 10 # Default function timeout in seconds
environment:
NODE_ENV: ${self:provider.stage} # Set environment variable for stage
BUCKET_NAME: ${self:custom.bucketName} # Dynamic S3 bucket name
vpc: # Optional VPC configuration
securityGroupIds:
- ${env:SECURITY_GROUP_ID}
subnetIds:
- ${env:SUBNET_ID}
iamRoleStatements: # Inline IAM permissions for the function
- Effect: "Allow"
Action:
- "s3:GetObject"
- "s3:PutObject"
Resource: "*"
- Effect: "Allow"
Action:
- "sns:Publish"
Resource: "*"
package:
exclude: # Exclude unnecessary files from the deployment package
- .git/**
- node_modules/**
- tests/**
include:
- src/** # Include source files
- lib/** # Include internal libraries
functions:
hello:
name: ${self:service}-${self:provider.stage}-hello # Dynamic function name
handler: handler.hello # Entry point for the Lambda function
memorySize: 512 # Custom memory size
timeout: 10 # Custom timeout
events:
- http:
path: users/create
method: get
cors: true # Enable CORS
- s3:
bucket: ${self:custom.bucketName}
event: s3:ObjectCreated:*
- sns:
topicName: ${self:custom.snsTopic}
custom:
bucketName: my-bucket-${self:provider.stage} # Dynamic bucket name for different stages
snsTopic: my-sns-topic-${self:provider.stage} # Dynamic SNS topic for different stages
resources:
Resources:
$ref: ../custom_resources.json # External JSON file for custom resources

This configuration file defines a hello function, which is triggered by HTTP requests, S3 object creation events, and SNS topics. The iamRoleStatements section allows your function to interact with S3 and SNS, while vpc enables you to secure your function in a VPC if needed.

Writing the Lambda Function

Now, let’s define the logic for the hello function. Open handler.js and replace the contents with the following:

module.exports.hello = async (event) => {

  return {

    statusCode: 200,

    body: JSON.stringify({

      message: 'Hello, World!',

      input: event,

    }),

  };

};

This simple Lambda function responds to HTTP GET requests with a JSON object containing a “Hello, World!” message. The event object passed to the function contains the request data (e.g., parameters, headers).

Deploying the Application

You’re ready to deploy your application once you’ve written your Lambda function and configured the serverless.yml file. Run the following command:

serverless deploy

This will:

1. Package your code.
2. Create the necessary AWS resources (Lambda functions, roles, etc.).
3. Deploy everything to your specified AWS region and stage.

Once the deployment is complete, you’ll see an output with the endpoint URL for your Lambda function.

Monitoring and Logs

After deployment, you can monitor the logs of your Lambda function using the following command:

serverless logs -f hello -t

This will tail the logs, allowing you to track the function’s behavior in real time

Conclusion

Building serverless applications using AWS Lambda and the Serverless Framework enables developers to focus on application logic without being burdened by infrastructure concerns. By following the steps outlined in this guide, you’ve created and deployed a fully functional serverless application.

This is just the beginning – future articles will cover advanced topics such as handling cold starts, cost optimization, and monitoring with AWS CloudWatch. With serverless architecture’s nearly infinite scalability and pay-as-you-go model, it’s the perfect tool for building modern applications efficiently and cost-effectively.

So, grab your keyboard, set up your environment, and start building your next serverless project today!

Final Thoughts

You can build efficient, scalable serverless applications by refining your serverless.yml configuration and following best practices for writing and deploying Lambda functions. Remember to monitor logs and optimize your functions as your project grows.

Ready to Scale Your Business with Serverless Architecture? Let CTO2B Help!

At CTO2B, we specialize in helping startups and enterprises leverage the power of cloud and serverless technologies. Whether you’re just getting started or looking to optimize your existing applications, our team of experts can guide you through every step of your cloud journey.

Contact us today for a free consultation and discover how serverless architecture can transform your business, reduce costs, and scale effortlessly!