How to Deploy AWS Lambda Using CDK: Simple Guide

To deploy a Lambda function using AWS CDK, define a lambda.Function in your CDK stack with the runtime, handler, and code location. Then run cdk deploy to create the Lambda in your AWS account.

Syntax

Use the lambda.Function construct from the AWS CDK library to define your Lambda function. You specify the runtime environment, the handler method, and the source code location.

• runtime: The language runtime, e.g., Node.js, Python.
• handler: The method AWS Lambda calls to start execution.
• code: The source code, usually from a local directory or inline.

javascript

const lambda = require('aws-cdk-lib/aws-lambda');

new lambda.Function(this, 'MyFunction', {
  runtime: lambda.Runtime.NODEJS_18_X, // runtime environment
  handler: 'index.handler',           // file and exported function
  code: lambda.Code.fromAsset('lambda') // path to code
});

Example

This example shows a complete CDK stack in JavaScript that deploys a simple Lambda function using Node.js 18 runtime. The Lambda code is stored in a local folder named lambda with an index.js file exporting a handler.

javascript

const cdk = require('aws-cdk-lib');
const lambda = require('aws-cdk-lib/aws-lambda');

class LambdaStack extends cdk.Stack {
  constructor(scope, id, props) {
    super(scope, id, props);

    new lambda.Function(this, 'MyLambdaFunction', {
      runtime: lambda.Runtime.NODEJS_18_X,
      handler: 'index.handler',
      code: lambda.Code.fromAsset('lambda')
    });
  }
}

const app = new cdk.App();
new LambdaStack(app, 'LambdaStack');
app.synth();

Output

Deploying stack LambdaStack...
✅  LambdaStack

Outputs:
(No outputs defined)

Common Pitfalls

Common mistakes when deploying Lambda with CDK include:

• Incorrect handler string format (should be filename.exportedFunction).
• Wrong runtime version causing incompatibility.
• Missing or incorrect code path in code.fromAsset().
• Not running cdk synth or cdk deploy after changes.

javascript

/* Wrong handler example */
new lambda.Function(this, 'BadHandler', {
  runtime: lambda.Runtime.NODEJS_18_X,
  handler: 'app.main', // 'app' file missing or wrong export
  code: lambda.Code.fromAsset('lambda')
});

/* Correct handler example */
new lambda.Function(this, 'GoodHandler', {
  runtime: lambda.Runtime.NODEJS_18_X,
  handler: 'index.handler', // matches index.js export
  code: lambda.Code.fromAsset('lambda')
});

Quick Reference

Remember these key points when deploying Lambda with CDK:

• Use lambda.Function construct.
• Set runtime to your language version.
• Specify handler as file.exportedFunction.
• Provide code with lambda.Code.fromAsset() pointing to your code folder.
• Run cdk deploy to create or update the Lambda.

Key Takeaways

Define your Lambda function using the lambda.Function construct with runtime, handler, and code.

Ensure the handler string matches your code file and exported function exactly.

Use lambda.Code.fromAsset() to point to your local Lambda code directory.

Run cdk deploy to create or update the Lambda function in AWS.

Check runtime compatibility and code path to avoid deployment errors.