1. A system comprising: a computing device comprising a processor; and a memory that stores computer-executable instructions that, when executed by the processor, cause the processor to perform operations comprising obtaining a routing scenario associated with a customer of a routing service, wherein the routing scenario specifies customer data that is to be accessed to determine a call handling decision when a call is received, wherein the customer data is stored at a customer data source that is remote from the computing device, obtaining a request to route the call, wherein the call is directed to a called device associated with the customer, and wherein the call is received from the calling party, obtaining, from the customer data source, customer data that is associated with the calling party and with the computing device, determining, based on the customer data, the call handling decision, and providing the call handling decision to a network to route the call.