I'd start with IBM because I wonder what servres Aplle uses for its pay -

''Each time a person hits the "buy" button on a smartphone app, he says, it triggers a cascade of transactions behind the scenes involving credit card approvals, inventory and billing systems. The z13 can process 2.5 billion transactions per day, IBM claims -- equivalent to "100 Cyber Mondays every day of the year."

<!--IDG.GPT.IMUCounter = IDG.GPT.IMUCounter + 1;IDG.GPT.addLazyloadedAd(IDG.GPT.getIMUSlotName(), "true");document.write(' <div id="' +IDG.GPT.getIMUSlotName() + '" class="">');IDG.GPT.defineGoogleTagSlot(IDG.GPT.getIMUSlotName(), [[320,50],[300,250],[300,50]]);document.write('</div> ');$('#' + IDG.GPT.getIMUSlotName()).responsiveAd({screenSize:'971 1115', scriptTags: []});//-->

IBM

Fraud detection is another big focus. The z13 will allow companies to analyze every transaction they process in near real-time to detect instances of fraud in banking, health insurance and other industries, according to Mauri. Today's mainframes allow health providers to analyze only about half their transactions that fast, he said. "We're guaranteeing you'll be able to do real-time analytics on 100 percent of transactions," he said.''

http://www.computerworld.com/article/2868457/ibms-new-z13-mainframe-eats-mobile-app-data-for-lunch.html

e