Jan Meppe

Machine learning engineer in love with building digital products.

3 minute read

In this little tutorial you will learn how to build out this infrastructure on AWS.

Specifically we will:

Let’s get started!

Step 1: Creating the API Gateway

Let’s create an API gateway

Now click on rest API

And give it a name

Now click on Create Resource and create a new resource. I call mine tmp-resource

This is what it should look like now

Step 2: Creating the Lambda

Let’s create a new Lambda

Make sure to set the runtime to Python. Give it a nice name. I call mine tmp-lambda-jan

Great job! You now have a lambda running!

Paste this code in the body of the lambda (taken from here)

import json
# Example data

data = {
    "items": [
        {"id": 1, "name": "Item 1", "price": 10.99},
        {"id": 2, "name": "Item 2", "price": 15.99},
        {"id": 3, "name": "Item 3", "price": 20.99},
    ]
}

def lambda_handler(event, context):
    # Determine the HTTP method of the request
    http_method = event["httpMethod"]
    # Handle GET request
    if http_method == "GET":
        # Return the data in the response
        response = {
            "statusCode": 200,
            "body": json.dumps(data)
        }
        return response

    # Handle POST request
    elif http_method == "POST":
        # Retrieve the request's body and parse it as JSON
        body = json.loads(event["body"])
        # Add the received data to the example data
        data["items"].append(body)
        # Return the updated data in the response
        response = {
            "statusCode": 200,
            "body": json.dumps(data)
        }
        return response

    # Handle PUT request
    elif http_method == "PUT":
        # Retrieve the request's body and parse it as JSON
        body = json.loads(event["body"])
        # Update the example data with the received data
        for item in data["items"]:
            if item["id"] == body["id"]:
                item.update(body)
                break
        # Return the updated data in the response
        response = {
            "statusCode": 200,
            "body": json.dumps(data)
        }
        return response

         # Handle DELETE request
    elif http_method == "DELETE":
        # Retrieve the request's body and parse it as JSON
        body = json.loads(event["body"])
        # Find the item with the specified id in the example data
        for i, item in enumerate(data["items"]):
            if item["id"] == body["id"]:
                # Remove the item from the example data
                del data["items"][i]
                break
        # Return the updated data in the response
        response = {
            "statusCode": 200,
            "body": json.dumps(data)
        }
        return response

    else:
        # Return an error message for unsupported methods
        response = {
            "statusCode": 405,
            "body": json.dumps({"error": "Method not allowed"})
        }
        return response

And make sure to click on Deploy

Now you have updated the code in the lambda and re-deployed it! Good job!

Now all that is left is that we must hook the lambda into our API because as it stands right now the API is a bit empty.

Step 3: Adding the lambda and testing

Going back to our API we can now create a method

Use Method Type ANY and set the lambda to the name that you just created.

This is what you should see right now.

There’s one important setting that you must change and that is the Lambda proxy integration must be set to true

What this setting does is that it allows your API gateway to actually forward the requests it gets. If you don’t set this to true then the Lambda won’t get the event that we need. Now you can deploy the API!

Create a new stage. Dev is fine.

Step 4: Testing

Now copy the Invoke URL

And use it to test it on postman.

If you for example, try to hit this URL


And you get 

```json
{
    "message": "Missing Authentication Token"
}

Make sure to use the right resource, which in my case is tmp-resource and not my-resource

Try again… and boom!

Step 5: Cleanup

Remove the API

Remove the Lambda

Wrapping up

In this tiny tutorial we implemented a small system on the cloud that combines the AWS API Gateway and a Serverless AWS Lambda. I hope you had as much fun as I did making this tutorial. While the system itself is simple and straightforward, I urge and encourage you to try and experiment with different setups, because this is the first stepping stone to building systems on the cloud that scale.

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