Yes. There are apps that allow you to control the odds and amount of times that a prize is awarded. You should modify this probability according to the amount of participants that sign up to the app. You can also determine the specific moment to award a prize so that only the user that registers at that time wins. Another option, for example, is to award one prize for every 10 users registered, or only to those who score a certain amount of points. Our customer support team can help you configure the Instant Prizes app according to your needs.