Chapter 7: Real-World Example #2

🌐 Call Lambda via API Gateway (HTTP)

Turn Your Lambda Functions Into HTTP APIs

In Chapter 6, we built a serverless CSV processing pipeline using S3, SNS, and SQS. But what if you want to trigger your Lambda functions directly from a web browser, mobile app, or external webhook?

That's where API Gateway comes in. Think of it as a web server that sits in front of your Lambda function. When someone makes an HTTP request to your API Gateway endpoint, it automatically forwards that request to your Lambda function and returns the response.

This approach is perfect for:

• 🚀 Rails integration - Call from your Rails controllers, background jobs, or services
• 🌐 Frontend integration - Call from JavaScript, mobile apps, or single-page applications
• 🔗 Webhooks - Receive data from external services like Stripe, GitHub, or Slack
• 🔌 Public APIs - Expose your serverless functions as REST endpoints
• 🧪 Easy testing - Test your functions with curl, Postman, or any HTTP client
• 🔄 Integration flexibility - Connect with systems that speak HTTP but not AWS

In this chapter, we'll build a complete HTTP API that wraps your Lambda function, complete with proper error handling and Rails integration.

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🎯 What We're Building

We'll create a simple but robust HTTP API that can:

• Handle POST requests to process data
• Provide a GET health check endpoint
• Return properly formatted JSON responses
• Handle errors gracefully
• Work seamlessly with Rails applications and external services

By the end, you'll have a Lambda function that can be called like any other REST API.