1. Introduction

In this tutorial, we will learn how to deploy a REST API on AWS and Azure. We will use the AWS Lambda and Amazon API Gateway on AWS, and Azure Functions and Azure API Management on Azure. By the end of this tutorial, you'll be able to host your API on either of these platforms and expose it to the outside world.

Prerequisites:
- Basic knowledge of REST APIs
- Basic knowledge of AWS and Azure
- An AWS and Azure account

2. Step-by-Step Guide

AWS

1. Create a Lambda function: AWS Lambda will run our code in response to HTTP requests. In the AWS console, navigate to Lambda and click on Create function. Fill in the details and hit Create function.

2. Create an API Gateway: In the AWS console, navigate to API Gateway and click on Create API. Select REST API and hit Build. Fill in the details and hit Create API.

3. Link Lambda and API Gateway: In the API Gateway console, create a new resource and a new method (GET, POST, etc.). For the integration type, select Lambda Function and choose the Lambda function you created earlier.

Azure

1. Create an Azure Function: Azure Functions will run our code in response to HTTP requests. In the Azure portal, navigate to Functions and click on Create. Fill in the details and hit Create.

2. Create an API Management instance: In the Azure portal, navigate to API Management services and click on Add. Fill in the details and hit Create.

3. Import the Azure Function into API Management: In the API Management instance, click on APIs in the left menu, then Add API, then Function App, and select the Azure Function you created earlier.

3. Code Examples

AWS

# This is a simple Python Lambda function
def lambda_handler(event, context):
    # The 'event' parameter contains information about the incoming request
    return {
        'statusCode': 200,
        'body': 'Hello, World!'
    }

This function simply returns a 200 status code and a body of "Hello, World!". When linked with API Gateway, it will respond to HTTP requests with this message.

Azure

// This is a simple C# Azure Function
public static async Task<IActionResult> Run(HttpRequest req, ILogger log)
{
    log.LogInformation("C# HTTP trigger function processed a request.");

    return new OkObjectResult("Hello, World!");
}

This function simply returns a 200 status code and a body of "Hello, World!". When imported into API Management, it will respond to HTTP requests with this message.

4. Summary

We have learned how to deploy a REST API on AWS and Azure. We used AWS Lambda and Amazon API Gateway on AWS, and Azure Functions and Azure API Management on Azure. Now you can expose your API to the world via either of these platforms.

5. Practice Exercises

1. Create a Lambda/Azure Function that returns your name instead of "Hello, World!". This will test your understanding of how to modify the code running on AWS Lambda/Azure Functions.

2. Create an API Gateway/API Management instance that responds to a different HTTP method (e.g., POST instead of GET). This will test your understanding of how to configure API Gateway/API Management.

3. Create an API that takes in a query parameter and returns it in the response body. This will test your understanding of how to handle incoming requests and modify the response.