Starbucks proves, once again, that it owns mobile payments.

The Seattle coffee giant now has 19 million active mobile app users in U.S. alone, Kevin Johnson, president and chief operating officer said, and mobile represented 24% of the total payments in 2Q.

The company’s Mobile Order & Pay program, launched last year, doubled in usage year-over-year, reaching 8 million transactions per month. Johnson said it’s just the tip of the iceberg:

We are just beginning to see the full benefit of Mobile Order & Pay beyond the speed and convenience it affords to both our customers and partners. Consider this: though still in its infancy, in 300 of our busiest urban stores, Mobile Order & Pay represents over 10% of transactions. And in those same stores at peak, Mobile Order & Pay represents nearly 20% of transactions. In Portland, where we first introduced Mobile Order & Pay in December of 2014, Mobile Order & Pay transaction volume in March was up approximately 150% from March of last year.

The success of the company’s mobile app (more than 80% of the app’s users have already upgraded to the new version, which was launched just last week) positions the company to successfully roll out its prepaid card, in collaboration with JPMorgan Chase and Visa, Johnson said.

A Starbucks general purpose prepaid Visa card will enable Starbucks Reward customers to earn Stars [coffee currency] everywhere Visa is accepted. That’s 40 million merchants worldwide. And where all stars earned can only be redeemed at Starbucks, we think this is a big win for our customers.

The program is slanted to launch by the end of this year. “Customers will be able to apply for the Starbucks Rewards Prepaid Card through the Starbucks Mobile App or Starbucks.com,” the company said late March. “This new model is just the beginning of Starbucks opening up its digital ecosystem as well as extending its payment platform.”