Abstract: Techniques are described for asynchronous communication of transaction data to client processes. A transaction request may be sent from a client process to a contract engine, which may perform multiple service calls to network services to generate transaction data for the transaction. The transaction data may be stored in an aggregate contract data object, and provided asynchronously to the client process for presentation via a user interface such as an e-commerce application. In some cases, the client process may, subsequently to the initial transaction request, send one or more requests for portions of the transaction data. Such requests may be sent asynchronously with respect to the initial transaction request. In some cases, the client process may provide callback information specifying a network location to which transaction data may be asynchronously communicated after it has been generated.

Abstract: Techniques are described for parallel processing of items, specified for purchase in a transaction. A transaction request may be received, specifying a plurality of items in a transaction. Multiple subsets of one or more items may be determined that are suitable for parallel processing by multiple instances of a network services, the subsets determined based on configuration information describing a parallel processing capability of the network service specified during registration. Multiple service calls may be made to cause the multiple instances of the network service to generate transaction data corresponding to the subsets. The transaction data may be incorporated into an aggregate contract data object on receipt, and provided to client process(es) for presentation via a user interface such as an e-commerce application.