Abstract: A system and method are disclosed for routing optimization. A gateway processing service receives a first ordered list of payment processing networks associated with a first condition. The first ordered list comprises a higher priority payment processing network and a lower priority payment processing network. A second ordered list received by the gateway processing service comprises a higher priority payment processing network and a lower priority payment processing network. An authorization request message for a transaction is received by the gateway processing service. If the first condition is satisfied, the gateway processing service routes the authorization request message according to the first ordered list. If the first condition is not satisfied, the gateway processing service routes the authorization request message according to the second ordered list.