A method comprising receiving, by a server computer, an authorization request for a transaction conducted with a payment token from a merchant via an open payment processing network. The payment token associated with an account having a no preset spending limit. The method also determines, by the server computer, an exposure limit of the account in real-time based on information obtained by the open payment processing network. The method also determines, by the server computer, whether or not to authorize the transaction based on the determined exposure limit.