Rob Reeg took over as president of MasterCard's Global Technology and Operations in May 2008, the de facto chief of IT at the $4 billion credit-card and electronic payment provider.

This is a glimpse into his new world: On behalf of 25,000 financial institutions, MasterCard's worldwide network in 2007 processed 18.7 billion transactions totaling some $2.3 trillion. On an hourly basis, the network has to manage 140 million transactions, with a response time of 140 milliseconds per transaction. And 99.999 percent network availability is standard operating procedure.

All of this wasn't totally new to Reeg. He had served in the position on an interim basis since January 2008. And before that he was MasterCard's CTO. "So it was a fairly easy transition," he says.

Though the transition may have been a piece of cake, his job's demands are anything but. Ridiculous network requirements aside, Reeg is responsible for managing MasterCard's global IT environment, headquartered in St. Louis and with operations in 210 countries, preventing frauds and credit-card scams, innovating with transaction-processing systems and enhancing financial institutions' product offerings gleaned from MasterCard's data warehouse. (To read more about MasterCard's IT innovation and what Reeg's predecessor did, see "IT-Led Innovation at MasterCard.")

CIO.com Senior Editor Thomas Wailgum talked to Reeg about his biggest worries, how his credit-card data got compromised, and just how "Priceless" his IT staff is.

What are your new responsibilities?

There are five key functions I'm focused on: 1. Our global network and how those 18.7 billion transactions flow. 2. Making sure we leverage that network to provide very fast, reliable payment processing. 3. On top of that platform, how do we provide our customers with custom and differentiated payment solutions. 4. How do we provide support to customers as they use our products and services. 5. How do we leverage that gold mine of data that occurs when you have 18.7 billion transactions that you're processing.

Who are MasterCard's customers?

Our customers are typically the banks. We're in what we call a four party model. There are card holders, who have a relationship with an issuing bank; so that's two parties in the model. On other side there are the merchants have a relationship with their bank, an acquiring bank. Those are the four primary stakeholders in any kind of payment transaction.