Just add a rotating endpoint for what ever plan the user purchases, for eg If the user purchases 1000 IPs, then provide an endpoint which can randomly pick any proxy form the 1000 I already purchased. The case is we don't need to manage it pragmatically on our side. Some companies like mine requires to give proper reason to use each proxy, so instead if there is a single endpoint, we can easily get access to a single endpoint and use the proxies as per our need.