This repository offers guidance on how to use an Amazon Cognito Userpool's custom SMS sender Lambda trigger to send OTP messages on WhatsApp when a user signs up.

Amazon Cognito lets you easily add user sign-up and authentication to your mobile and web apps. Amazon Cognito works with external identity providers that support SAML or OpenID Connect, social identity providers (such as Facebook, Twitter, Amazon) and you can also integrate your own identity provider.

By default, Amazon Cognito uses Amazon Simple Notification Service (Amazon SNS) for delivery of SMS text messages. This can be changed with the help of custom SMS sender trigger. When you assign a custom SMS sender trigger to your user pool, Amazon Cognito invokes a Lambda function instead of its default behavior when a user event requires that it send an SMS message. With a custom sender trigger, your AWS Lambda function can send SMS notifications to your users through a method and provider that you choose. This This guide will walk you through the process of implementing custom SMS sender Lambda triggers to send one-time password (OTP) messages for user sign up via WhatsApp.