Amazon Cognito
Developer Guide (Version Last Updated: 07/28/2016)

Specifying a User Pool Name

You must specify a Pool Name for your Amazon Cognito user pool in the AWS Management Console. The name cannot be changed after the user pool is created.

Pool names must be between one and 128 characters long. They can contain uppercase and lowercase letters (a-z, A-Z), numbers (0-9), and the following special characters: + = , . @ and -.