Amazon Cognito now supports account recovery method prioritization
Amazon Cognito now supports recovery method prioritization, making it easier for developers to customize the flow users experience when they forget their passwords. Developers can specify whether they prefer that users receive a recovery code via SMS or email, and whether they would like to fall back to SMS or email if a verified phone number or email address is not available. This feature is available now in Amazon Cognito User Pools at no additional cost.
Source:: Amazon AWS