Cognito pre signup lambda timeout

Hi, I am trying to use pre-signup lambda for validation of user sign up. My lambda function will run more than 12s and not possible to optimize more than that. while testing through the hosted UI, I am experiencing lambda time out less than 5 to 7s (not sure provided approx.) is there any limitation on the service side of Cognito (or) is there any configuration that I possibly missed.

If it is service limitation how to proceed further and overcome the issue.