Abstract: A computer-implemented method, to facilitate processing a payment for an online transaction, includes, responsive to receiving secure transaction data from a merchant server, using a payment processor to generate a transaction data identifier to identify the transaction data. The payment processor communicates the transaction data identifier to the merchant server. In response to receiving a request to process a payment, including the transaction data identifier, the payment processor requests user credentials from a user. Upon receiving user credentials from the user, the payment processor verifies the user credentials. The payment processor processes the payment and generates a payment identifier to identify payment data associated with the payment. The payment processor communicates the payment identifier to the merchant server.

Abstract: A server system facilitates an exchange of messages with a remote client application. The server system includes a plurality of application servers hosting a plurality of applications. A plurality of Application Program Interfaces (APIs) provides programmatic access to the plurality of applications, each of the APIs being configured to receive request messages compiled by the remote client application. First and second request messages, respectively addressed to first and second APIs of the plurality of APIs by a remote client application, each comprise at least one common data component. Further, the first request message includes a first payload specific to the first API, and the second request message includes a payload specific to the second API.