Cognito POST confirmation trigger wokring?

The post-confirmation Lambda trigger in Amazon Cognito is designed to be invoked after various confirmation events, including both sign-up and authentication. While you can't directly disable specific trigger sources within the same Lambda function, you can implement logic in your Lambda function to handle different trigger sources differently.

To focus only on the POST_CONFIRMATION_SIGNUP trigger and ignore others like POST_CONFIRM_AUTHENTICATION, you can add a condition in your Lambda function to check the trigger source. Here's an approach you can take:

1. In your Lambda function, check the 'triggerSource' field in the event object.
2. If the triggerSource is 'PostConfirmation_ConfirmSignUp', proceed with your desired logic.
3. For all other trigger sources, simply return the event object without performing any actions.

This way, your function will effectively ignore the POST_CONFIRM_AUTHENTICATION and any other unwanted triggers, while still responding to the POST_CONFIRMATION_SIGNUP trigger as intended.

Here's a basic example of how you might structure your Lambda function:

exports.handler = (event, context, callback) => {
    if (event.triggerSource === 'PostConfirmation_ConfirmSignUp') {
        // Your custom logic for sign-up confirmation goes here
        // ...
    }
    // For all other trigger sources, just return the event
    callback(null, event);
};

This approach allows you to maintain a single Lambda function for the post-confirmation trigger while effectively focusing only on the sign-up confirmation event.

Remember, it's important to always return the event object to Amazon Cognito, even if you're not performing any actions for certain trigger sources. This ensures that the Cognito workflow continues smoothly for all scenarios.

Sources
Post confirmation Lambda trigger - Amazon Cognito
How can I issue an access token immediately after account confirmation in AWS Cognito without requiring the user to log in again? | AWS re:Post