Visa is the world's second-largest card payment organization (debit and credit cards combined), after being surpassed by China UnionPay in 2015, based on annual value of card payments transacted and number of issued cards. Because UnionPay's size is based primarily on the size of its domestic market, Visa is dominant in the rest of the world outside of China, with 50% market share of global card payments minus China.
Visa has operations across all continents worldwide with the exception of Antarctica. Nearly all Visa transactions worldwide are processed through VisaNet at one of four secure facilities. The data centers are located in Ashburn, Virginia, Highlands Ranch, Colorado, London, and Singapore. The data centers are heavily secured against natural disasters, crime, and terrorism; can operate independently of each other and from external utilities if necessary; and can handle up to 30,000 simultaneous transactions and up to 100 billion computations every second. Every transaction is checked past 500 variables including 100 fraud-detection parametersÃ¢ÂÂsuch as the location and spending habits of the customer and the merchant's location Ã¢ÂÂ before being accepted.