Integrating Lambda with API Gateway
Configure API Gateway to trigger your Lambda functions, creating a complete serverless HTTP endpoint.
Integrating Lambda with API Gateway is a free Serverless Backend with AWS Lambda & API Gateway lesson on CoddyKit — lesson 3 of 4. You can read the complete lesson below for free — then practise it hands-on in the browser with a built-in code editor and a 24/7 AI tutor. It is part of the Serverless Backend with AWS Lambda & API Gateway learning path, one of 4 lessons in the course, and your progress syncs across the web and the CoddyKit app.
Connect Lambda to API Gateway
Welcome! In this lesson, you'll learn how to link your AWS Lambda functions to API Gateway. This creates a powerful serverless HTTP endpoint, letting users trigger your code via web requests.
Think of it as giving your Lambda function a web address!
API Gateway: Your Web Front Door
Remember, API Gateway acts as the front door for your serverless applications. It handles incoming HTTP requests and routes them to the correct backend service, like a Lambda function.
- Manages traffic efficiently
- Handles authentication and authorization
- Routes requests to specific functions
The Lambda Proxy Integration
The most common and flexible way to connect API Gateway to Lambda is using Lambda Proxy Integration. This method passes the entire incoming HTTP request to your Lambda function.
Your Lambda then processes the request and returns a specific JSON response that API Gateway understands.
Request & Response Format
With proxy integration, API Gateway sends the full HTTP request (headers, body, query parameters) to your Lambda as an event object.
Your Lambda must return a JSON object with specific keys: statusCode, headers, and body. This allows API Gateway to craft the final HTTP response for the client.
Our First Proxy Lambda
Let's write a simple Python Lambda function that expects a proxy event. It will return a 'Hello from Lambda!' message and echo back part of the input.
Remember, the event dictionary contains all request details.
import json
def lambda_handler(event, context):
# The 'event' contains details like
# path, httpMethod, headers, body, queryStringParameters
print(f"Received event: {json.dumps(event)}")
# Prepare the response body
response_body = {
"message": "Hello from Lambda! Your path was:",
"path": event.get("path", "N/A")
}
# Return the response in the required proxy format
return {
"statusCode": 200,
"headers": {
"Content-Type": "application/json"
},
"body": json.dumps(response_body)
}Setting Up API Gateway
Now, let's set up the API Gateway part. We'll create an HTTP API and define a route.
HTTP APIs are simpler and more cost-effective for basic serverless endpoints compared to REST APIs. We covered the differences in a previous lesson.
Defining a Route & Integration
In API Gateway, you'll create a route, for example, GET /hello. This route specifies the HTTP method and path for your endpoint.
Then, you'll add an integration to this route, pointing it to your Lambda function. This is where API Gateway knows which Lambda to invoke!
Granting Invoke Permissions
For API Gateway to successfully trigger your Lambda function, it needs permission. This is managed by an IAM Role associated with API Gateway.
Specifically, API Gateway requires the lambda:InvokeFunction permission on your Lambda resource. AWS often sets this up automatically when integrating via the console.
Deploy & Test Your Endpoint
After configuring the route and integration, you need to deploy your API Gateway changes. This makes your endpoint publicly accessible.
You'll get an invoke URL, which you can use with tools like a web browser or curl to test your new serverless API!
Integration Check
You've learned how Lambda Proxy Integration works. Which of the following are REQUIRED in the JSON response from a Lambda function for API Gateway Proxy Integration?
Recap: Lambda & API Gateway
Great job! You've learned how to integrate Lambda functions with API Gateway:
- API Gateway acts as the web front door for your serverless functions.
- Lambda Proxy Integration is the standard method, passing full HTTP requests to Lambda.
- Lambda returns a specific JSON format (
statusCode,headers,body) for API Gateway to process. - IAM permissions are crucial for API Gateway to invoke your Lambda function securely.
- After deployment, your Lambda function is accessible via a public URL!
Frequently asked questions
Is the “Integrating Lambda with API Gateway” lesson free?
Yes — the full text of “Integrating Lambda with API Gateway” is free to read here on the web, and the Serverless Backend with AWS Lambda & API Gateway course includes 4 lessons in total. To practise it interactively (a built-in code editor and a 24/7 AI tutor) and unlock the rest of the Serverless Backend with AWS Lambda & API Gateway course, upgrade to CoddyKit PRO.
What will I learn in “Integrating Lambda with API Gateway”?
Configure API Gateway to trigger your Lambda functions, creating a complete serverless HTTP endpoint. You practise Serverless Backend with AWS Lambda & API Gateway with hands-on code you run directly in the browser, and a 24/7 AI tutor answers your questions as you work through the lesson.
Do I need any experience to start Serverless Backend with AWS Lambda & API Gateway?
No prior experience is required. Serverless Backend with AWS Lambda & API Gateway on CoddyKit is structured for beginners through advanced learners; this is — lesson 3 of 4, so you can start here or from the beginning and move at your own pace.
How long does the “Integrating Lambda with API Gateway” lesson take?
Most CoddyKit lessons take about 5–10 minutes. Each one is bite-sized and interactive, so you make steady progress and pick up exactly where you left off across the web and the app.
Can I write and run code in this Serverless Backend with AWS Lambda & API Gateway lesson?
Yes. Every Serverless Backend with AWS Lambda & API Gateway lesson includes a built-in code editor, so you write and run real code right in your browser and get instant AI feedback — no local setup required.
All lessons in this course
- Introduction to API Gateway
- HTTP API vs. REST API
- Integrating Lambda with API Gateway
- Request and Response Mapping in API Gateway