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Gopi Krishnan VM
Gopi Krishnan VM

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How to Build a Secure & Scalable Serverless REST API with AWS Lambda & API Gateway


Building a serverless API can seem overwhelming, but AWS makes it easy with Lambda and API Gateway. In this guide, we’ll explore how to build a scalable and secure API step by step.

What is AWS Lambda?

AWS Lambda is a serverless compute service that allows you to run code only when needed. Think of it as a vending machine — it only operates when someone interacts with it, saving you money and resources.

Why Do We Need API Gateway?
You might wonder, why use API Gateway if Lambda has Function URLs?

The answer is security, flexibility, and scalability. API Gateway lets you:
✅ Secure APIs with IAM, API Keys, and JWT authentication
✅ Handle multiple HTTP methods like GET, POST, and DELETE
✅ Apply rate limiting & request validation

Steps to Build a Serverless REST API
Step 1: Create a Lambda Function
First, we create a Lambda function that returns a JSON response when triggered.

Step 2: Set Up API Gateway
Next, we create an HTTP API in API Gateway and connect it to Lambda. This lets users send requests via a public URL.

Step 3: Secure the API with a Lambda Authorizer
For added security, we use a Lambda Authorizer to restrict access to authenticated users only.

Final Thoughts
AWS Lambda and API Gateway make it easy to build scalable, cost-effective APIs. Whether you’re a beginner or an expert, serverless architectures can streamline development and reduce costs.

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