Cognito Triggers with Lambda

1. Introduction

AWS Cognito is a service that provides authentication, authorization, and user management for web and mobile applications. Cognito Triggers allow you to run AWS Lambda functions in response to specific events in the Cognito user pool lifecycle.

2. Cognito Triggers

Cognito supports several triggers that can be associated with specific events:

• Pre Sign-up
• Post Confirmation
• Pre Authentication
• Post Authentication
• Custom Message
• User Migration
• Pre Token Generation
• Define Auth Challenge
• Create Auth Challenge
• Verify Auth Challenge Response

3. Lambda Functions

Lambda functions are serverless compute services that run your code in response to events and automatically manage the underlying compute resources. Here’s an example of a Lambda function for a Pre Sign-up trigger:

    const AWS = require('aws-sdk');

    exports.handler = async (event) => {
        // Custom logic for pre-signup
        if (event.triggerSource === 'PreSignUp_ConfirmSignUp') {
            // Example: Check if the email is already in use
            const email = event.userName;
            // Your logic to validate the email...
        }
        return event;
    };
    

4. Setting Up Cognito Triggers with Lambda

1. Create a Cognito User Pool in the AWS console.
2. Navigate to the "Triggers" tab in the User Pool settings.
3. Choose a trigger type (e.g., Pre Sign-up).
4. Select the Lambda function you want to associate with the trigger.
5. Deploy the Lambda function.

5. Best Practices

• Keep your Lambda functions lightweight and focused on a single task.
• Use environment variables to manage configuration settings.
• Implement error handling in your Lambda function to manage failures gracefully.
• Monitor and log your Lambda functions using CloudWatch for debugging and performance insights.

6. FAQ