Serverless computing has revolutionized the way developers build scalable and cost-effective applications. By removing the need to manage infrastructure, teams can focus more on writing code instead of provisioning servers. One of the most popular platforms for building serverless applications is Amazon Web Services (AWS), particularly with services like AWS Lambda and Amazon API Gateway. This tutorial provides a detailed, step-by-step process to create a serverless web application using AWS Lambda and API Gateway.

Why Go Serverless?

Traditional server-based architectures require ongoing maintenance, scaling strategies, and infrastructure monitoring. In contrast, serverless platforms like AWS Lambda offer:

  • Automatic Scaling: Handles millions of events and scales transparently.
  • Pay-as-You-Go: Charges apply only when code is executed.
  • No Server Management: Developers never have to provision or manage physical or virtual servers.

Prerequisites

Before starting, ensure you have the following:

  • An active AWS account
  • Node.js or Python installed (for Lambda function development)
  • AWS CLI configured on your local environment
  • Basic knowledge of REST APIs and HTTP methods

Step 1: Create an AWS Lambda Function

Log in to the AWS Management Console and navigate to the Lambda service.

  1. Click on “Create function”
  2. Select “Author from scratch”
  3. Enter a function name (e.g., MyServerlessFunction)
  4. Choose a runtime (Node.js, Python, etc.)
  5. Click “Create function” at the bottom

Once the function is created, scroll down to the code editor and add your function logic. Here’s a simple example using Node.js:

exports.handler = async (event) => {
    const response = {
        statusCode: 200,
        body: JSON.stringify('Hello from Lambda!'),
    };
    return response;
};

Click Deploy to save the changes to your function.

Step 2: Create an API Using Amazon API Gateway

Amazon API Gateway is a fully managed service that makes it easy to create and publish RESTful APIs.

  1. Navigate to API Gateway from the AWS Console
  2. Click “Create API”
  3. Choose “HTTP API” for greater simplicity and performance
  4. Under Integrations, choose Lambda and select the Lambda function created earlier
  5. Configure a route (e.g., GET /hello)
  6. Deploy the API and note the endpoint URL

Visit the deployed endpoint in a browser or tool such as Postman, and you’ll see the response from your Lambda function.

Step 3: Add More Functionality

Now that your basic serverless API is up and running, extend its capabilities. You can implement CRUD operations by creating separate Lambda functions for each HTTP method and integrating them through API Gateway.

Example: POST Request

Add a new Lambda function to handle data submission:

exports.handler = async (event) => {
    const requestBody = JSON.parse(event.body);
    const name = requestBody.name || 'Anonymous';
    return {
        statusCode: 200,
        body: JSON.stringify(`Welcome, ${name}!`),
    };
};

Set up an API Gateway route POST /welcome, and integrate it with the new function following the same steps as before.

Step 4: Enable CORS

By default, API Gateway doesn’t allow cross-origin requests. For enabling web applications hosted on different domains to access your API, enable CORS:

  1. Under your API in API Gateway, go to the Routes section
  2. Select the route you want to enable CORS for
  3. Click on “Enable CORS”
  4. API Gateway will automatically add the necessary headers

Step 5: Deploy a Static Frontend

Pair your serverless backend with a static frontend. AWS S3 can host your HTML, CSS, and JavaScript files.

  1. Go to S3 and create a new bucket
  2. Upload your web app files (including an index.html)
  3. Enable static website hosting
  4. Set the bucket policy to allow public reads

Update your frontend’s AJAX requests to use the deployed API Gateway URL for data retrieval and submission.

Step 6: Secure Your API

Security is critical for production applications. You can secure your API with the following techniques:

  • API Keys: Require a key to access routes
  • IAM Roles: Use Identity and Access Management for finer control
  • Amazon Cognito: Implement authentication with user pools and identity pools

These features are configurable within API Gateway under the “Authorization” options when setting routes and stages.

Step 7: Monitor and Debug

Use AWS CloudWatch for monitoring all Lambda function logs and performance metrics.

  • Each Lambda invocation automatically logs to CloudWatch
  • You can add console.log() statements to debug in real-time
  • Set up CloudWatch Alarms for error rates and request thresholds

Conclusion

Building serverless applications with AWS Lambda and API Gateway empowers developers to deploy fast, scale efficiently, and reduce operational overhead. By following this tutorial, you’ve learned how to set up Lambda functions, expose them via RESTful APIs, enable CORS, and connect a static frontend. By combining AWS services effectively, it’s possible to launch highly functional web applications without ever managing servers.

FAQ

Q1: What programming languages can I use with AWS Lambda?

AWS Lambda officially supports Node.js, Python, Java, Go, Ruby, and .NET. You can also use custom runtimes for other languages.

Q2: Is AWS Lambda truly “serverless”?

Yes, AWS abstracts away the server infrastructure, allowing developers to execute functions without provisioning or managing servers.

Q3: Are there limitations on AWS Lambda?

Yes. Lambda has a maximum execution timeout of 15 minutes, limited memory and storage, and concurrency limits depending on your AWS account.

Q4: Can API Gateway handle real-time communication?

For real-time use cases, consider WebSocket APIs in API Gateway or services like AWS AppSync for GraphQL-based real-time data.

Q5: How do I test my Lambda function locally?

You can use the AWS SAM CLI to simulate function invocation locally using your terminal and test events in JSON format.