1. A method comprising: accessing a transaction request describing a transaction to purchase a plurality of items, the transaction request entered through an e-commerce application, the transaction request sent by a client configured to determine content to be presented within the e-commerce application; performing a plurality of calls to cause a plurality of network services to execute to generate a plurality of data objects comprising transaction data regarding the transaction; on receiving individual ones of the plurality of data objects from the plurality of network services, incorporating the individual ones of the plurality of data objects into an aggregate contract data object; and asynchronously with respect to the transaction request, providing to the client at least a portion of the transaction data stored in the aggregate contract data object, the providing comprising one or more of: providing at least the portion of the transaction data to the client in a synchronous response to a request from the client; or asynchronously providing the transaction data stored in the aggregate contract data object to the client using callback information provided by the client in the transaction request, the callback information indicating a network location of the client.