Card issuing and processing startup Marqeta may not have picked the sexiest part of the payments ecosystem to disrupt, but it’s looking to catch the same wave as challenger banks and fintech lenders that are raking in funds by the hundreds of millions as they expand into new geographies.

Marqeta uses open APIs to allow companies like payments firms Square and Klarna and lending platforms Affirm and Kabbage to create customized payment cards for their customers. The Oakland, Calif.-based company, founded in 2010, raised $260 million in a Series E round in May. It’s now valued at more than $2 billion and on track for an initial public offering.

Jason Gardner, founder and CEO of Marqeta, said the company builds for builders, and the digital banks and fintech lenders eating into the business of traditional banks are some of the most active builders out there.

Capital on Tap, a U.K.-based startup that provides fast funding to small businesses, announced on Tuesday that it tapped Marqeta to power payment processing for its small business credit card. Since its launch in 2012, Capital on Tap provided close to £1 billion ($1.25 billion) in funding to more than 60,000 small businesses across the U.K.

Marqeta’s European Digital Banking solution, rolled out in April, allows clients to build, test and refine new features in a developer sandbox. It supports instantly issued virtual cards and advanced spending controls and provides customers access to real-time transaction data. Digital-only bank clients include France-based Morning, which is using Marqeta to strengthen its real-time core banking platform for B2C and B2B customers, and Switzerland-based YAPEAL, which is using the company’s lean processing capabilities to build a private account offering and card payment product. YAPEAL is expected to launch sometime in the third quarter.

In the U.S., Marqeta powers Square Cash Card and all the features and functionalities that go around that. “Digital banks are a big focus for us,” Gardner said. “We have a whole practice around it, and there are a number of companies that already operate on our platform. We focus on other areas like e-commerce, travel, disbursements, lending and on-demand delivery, but digital banking is definitely one area where we’re focused on building for builders.”

Almost half (49%) of respondents to a survey by Marqeta, released in February, said they would consider switching their banking business to a digital-only bank. Additionally, Europeans are 2.5 times more likely than someone in the U.S. to already be using a digital bank. Marqeta currently operates in the U.S., Canada and Europe and is eyeing entries into Asia, Latin America and Africa.

Gardner said card processing is a $45 trillion global market that’s on its way to becoming $80 trillion over the next 10 years. In the meantime, companies are changing the way they do business. “Many companies in the future will either be developer-led or product-led, and design thinking and how they build their products is going to be core to their offerings,” he added. “Calling your bank to build a card just isn’t going to work anymore.”

Marqeta’s rapid growth is the result of the platform’s easy user experience and developer-friendly interface, payments consultant David True previously told Bank Innovation. “It’s about simplicity,” he said. “They’ve made it very easy to turn on card issuing, whereas in the past you would have to find a bank to work with you.”