Hello World Serverless : Deploy an AWS Lambda Function with CDK and TypeScript

Serverless has become one of the most popular approaches for building fast, scalable and cost-effective applications. With AWS Lambda you only focus on writing code and AWS takes care of everything else: scaling, servers and availability.

But there is a tool taht makes the experiences even better : AWS CDK. It allows you to define your infrastructure using familiar programming languages such as TypeScript, Java, Python,C# or Go, instead of writing raw of CloudFormation template.

In this article, I’ll show you how to deploy your very first **AWS lambda function ** in just a feew minutes using AWS CDK and TypeScript. No complex architecture, no heavy prerequistes but just a simple and solid first step into the serverless world.

Prerequistes

Before getting started, make sure you have:

• Node.js installed
• AWS CLI configured :

aws configure

• AWS CDK installed globally:

npm install -g aws-cdk

• An active AWS account

1. Initialize the SDK project

Create a new directory for your project:

mkdir cdk-lambda-demo
cd cdk-lambda-demo

Initialize a TypeScript CDK application:

cdk init app --language typescript

CDK generates the following structure:

/bin    --------------> application entry
/lib    --------------> CDK stack definitions
cdk.json -------------> CDK configuration
tsconfig.json
package.json

2. Create the lambda function

Create a /lambda/ folder and a hello.ts file:

mkdir lambda
touch lambda/hello.ts

Add the following code to hello.ts

//lambda/hello.ts

export const handler = async()=> {
    return {
        statusCode: 200,
        body: JSON.stringify({message: "hello world from aws cdk "});
    }
};

This Labda function simply return a JSON response with a message.

3. Declare the lambda function in CDK Stack

Open lib/cdk-lambda-demo-stack.ts and replace its content with:

import * as cdk from "aws-cdk-lib";
import { Construct } from "constructs";
import * as lambdaNodejs from 'aws-cdk-lib/aws-lambda-nodejs';

export class CdkLambdaDemoStack extends cdk.Stack {
  constructor(scope: Construct, id: string, props?: cdk.StackProps) {
    super(scope, id, props);

     new lambdaNodejs.NodejsFunction(
      this,
      'HelloHandler', { 
      entry: 'lambda/hello.ts', // path to the Lambda function code
      handler: 'handler',
      functionName: 'HelloHandler' // name of the exported handler function
    });
  }
}

Explanation:

• runtime -> execution environment (Node.js 18 by default)
• code -> dpath to the lambda source file
• handler -> exported handler function
• functionName -> lambda name used when invoking it via aws cli

4. Deploy the Lambda function

Before deploying install dependencies and boostrap CDK:

npm install  
cdk bootstrap
cdk synth   # generates the cloudFormation template

cdk deploy # deploys the stack

5. Test the Lambda function

Using the AWS cli:

aws labda invoke\
-- function-name HelloHandler \
response.json

Then display the response:

cat response.json

From aws console:

6. Clean up resources

cdk destroy

This removes The Lambda function and all related CDK resources.