In this section, we will look at the architecture and requirements of building a serverless microservice. The rest of the chapter is heavily hands-on in terms of configuration in the AWS Management Console, but also Python code. The Python code follows basic design patterns and is kept simple, so that you can understand and easily adapt it for your own use cases.

We want to create a microservice that is able to serve a web visits count, for a specific event, of the total users browsing your website.

We will be signing into the AWS Management Console. The reason we are using the Management Console first is to give you a better understanding of how Lambda functions work, and how they integrate with the other AWS services, such as API Gateway and DynamoDB. In later chapters, we will show you how to deploy Lambda functions using the AWS CLI. If you are a first-timer to Lambda, then I always find it useful to first create a full serverless stack manually in the Management Console to gain a better and deeper understanding than, say, have a magic command spin up the full AWS infrastructure!

We are going to first use the AWS Management Console to create the Lambda IAM role and policies, so that the Lambda function can access DynamoDB, and also write any logs or any statuses to CloudWatch. The Management Console, which we used...

We are going to look at creating a DynamoDB table, writing data to the table from hardcoded values, writing data records from a file, and then we are going to show two different ways to query a table:

The following steps show how to create a DynamoDB:

1. You need to sign in to the AWS Management Console first and then open the AWS DynamoDB console at https://console.aws.amazon.com/dynamodb/.
2. Choose Create table or, in the DynamoDB navigation pane, choose Tables and choose Create table.
3. In the Create DynamoDB Table window, perform the following steps:
   1. Under Table name, type user-visits
   2. In Primary key for Partition key, type EventId and...

Now that we understand how to create a table, add data, and query DynamoDB using the AWS Console, we will look at how we can do this using only Python code.

We recommend you use a Python Integrated development environment (IDE) such as Eclipse PyDev (http://www.pydev.org/download.html) or PyCharm (https://www.jetbrains.com/pycharm/). You do not need to use an IDE, but I would recommend that you do. If you really want to, you can use VI, for example, on Linux to actually edit your code. But using an IDE allows you, for example, to run debugging or set up unit testing locally and step through it, which makes it easier and more productive for development.

First create the table using Boto3 https://boto3.readthedocs.io/ in Python. Run the code in the following section in PyCharm or your favorite text editor...

Now that we have the security and user-visits table set up with some data, and know how to write code to query that DynamoDB table, we will write the Lambda Python code.

Now we have the IAM role with two IAM policies attached, create the Lambda function itself. Here, we are creating a function from scratch, as we want to walk through the full details to deepen your understanding of what is involved in creating a serverless stack. The following diagram shows data API architecture involving CloudWatch, DynamoDB, IAM, and Lambda:

Perform the following steps:

1. Sign in to the AWS Management Console and open the AWS Lambda console at https://console.aws.amazon.com/lambda/...

Now that we know the Lambda function works with some API Gateway test data, and returns a header and body with a statusCode of 200, we just need to add the API Gateway that will invoke the Lambda function, as shown in the following diagram:

Perform the following steps:

1. Sign in to the AWS Management Console and open the API Gateway console at https://console.aws.amazon.com/apigateway/.
2. Choose Get Started or, in the Amazon API Gateway navigation pane, choose APIs and choose Create API.
3. On the Create page, perform the following steps:
   1. In Choose Protocol, select REST
   2. In Create new API, select New API
   3. Under Settings, type metrics for API name
   4. Choose Regional for Endpoint Type
   5. Choose Create API
4. Choose Create Resource from the Actions drop-down menu.
5. In the New Child Resource window, perform the following steps...

Now that we know the API Gateway integration with the Lambda function works, we will deploy it and get the URL. The architecture is shown in the following diagram:

The workings of this architecture is as follows:

1. Sign in to the AWS Management Console and open the API Gateway console at https://console.aws.amazon.com/apigateway/.
2. In the Amazon API Gateway navigation pane, choose APIs and metrics.
3. Select Resources under metrics and /Vists/{resourceId}, and choose Deploy API from the Actions drop-down menu.
4. In the Deploy API pop-up window, perform the following steps:
   
   1. In Deployment stage, choose [New Stage]
   2. In Stage name, type prod
   3. In Stage description, type prod
   4. Select Deploy
5. The Stages under metrics should be automatically selected on the left-hand menu.
6. Select GET under prod/visits/{resourceId}/GET to get the invoke URL. The invoke...

You will need to delete the resources manually. I recommend you use the AWS Console to do so. Perform the following steps:

1. Deleting API Gateway:
   1. Log on to the Console at https://console.aws.amazon.com/apigateway/
   2. Choose Resource under metrics on the left-hand APIs menu
   3. Choose Delete API from the Actions drop-down menu
   4. Type metrics in the Enter the name of the API before confirming this action textbox
   5. Choose Delete API
2. Deleting the DynamoDB table:
   1. Log on to the Console at https://console.aws.amazon.com/dynamodb/
   2. Choose Tables on the left-hand DynamoDB menu
   3. Choose user-visits
   4. Choose Delete table
   5. Choose Delete

3. Deleting the Lambda function:
   1. Log on to the Console at https://console.aws.amazon.com/lambda/
   2. Choose Functions on the left-hand AWS Lambda menu
   3. Choose lambda-dynamo-data-api
   4. Choose Delete function under the Actions menu
   5. Choose Delete
4. Deleting...

In this chapter, we have discussed security and why it is important. Applying the OWASP security by design principles is a good first step to ensure that your serverless stack is secure. We then discussed IAM roles and gave an overview of policies, explaining how they are the key documents to ensure restricted access to AWS resources. We then looked at an overview of some of the security concepts and principles regarding securing your serverless microservices, specifically regarding Lambda, API Gateway, and DynamoDB.

We then built a scalable serverless microservice with a RESTful data API. We started by creating a DynamoDB table, then added data to it, and queried it, first using the AWS console manually, then using the Python Boto3 SDK. We then built a simple Lambda to parse the request URL parameters, query DynamoDB, and return the records as part of a response body....