✅ - Verifying existing user with attributes

[vestal chasm]

I have login mechanism that lets you sign in with email with username as an attribute. During signup, how can I check if there is already a user with a given username.

[vapid stratus]

There is no solution out of the box that is available to resolve this issue.

However, there are some interesting lambda triggers that are available and you can take a look, if it can solve your problem. https://docs.aws.amazon.com/cognito/latest/developerguide/cognito-user-identity-pools-working-with-aws-lambda-triggers.html

You can specifically explore the Pre sign-up Lambda trigger (https://docs.aws.amazon.com/cognito/latest/developerguide/user-pool-lambda-pre-sign-up.html)

You can also rely on the user already exists error from Cognito.. User already exists (which would be contingent on how you have Cognito setup)

[night ledge]

✅ - Verifying existing user with attributes