New pattern submission - Cognito-Lambda-DynamoDB

[proton0210]

Description
This pattern demonstrates the process of creating a user in Amazon Cognito, handle a Post Confirmation trigger with AWS Lambda, and store user details in Amazon DynamoDB.

Language:
Typescript

Framework
CDK

Services from/to
Cognito to Lambda* to DynamoDB

• Lambda only gets triggered when user confirms their email

Description
This pattern demonstrates how to connect Amazon Cognito, AWS Lambda, and Amazon DynamoDB to automate user data storage when new members sign up. First, a user registers with Amazon Cognito, which manages user authentication flows and account verification. As soon as the user confirms their account, Cognito automatically triggers a “Post Confirmation” event. In response, AWS Lambda intercepts this event, extracting essential user attributes such as the user’s unique identifier (sub), email address, and any custom attributes—for example, first and last name fields. The Lambda function then inserts these details into a DynamoDB table, creating a permanent record of the user. DynamoDB’s serverless nature handles variable traffic automatically, while its pay-per-request billing model ensures you only incur costs for actual read/write requests.

By adopting this workflow, developers can drastically reduce manual integration efforts. Rather than writing custom logic to synchronize new user registrations with a database, the event-driven pattern offers a clean, serverless approach that supports high availability and resilience. All infrastructure is defined as code—using AWS Cloud Development Kit (AWS CDK) or an equivalent—so the entire setup, from the Cognito User Pool to the DynamoDB table, is version-controlled and easily replicable across different environments. You can enhance security further by applying least-privilege policies, restricting the Lambda function’s permissions to only those needed for inserting items into DynamoDB. In addition, you can add or modify user attributes quickly by updating the Lambda code, with zero downtime. This seamless solution also facilitates comprehensive end-to-end testing: once you confirm a new user, you simply check the DynamoDB table for the corresponding record. Overall, the pattern provides a cost-effective, scalable, and easily maintainable architecture for any application that requires automatic, post-sign-up data handling.

GitHub PR for template: 2704