Financial services giant Visa (V  ) announced on Monday that they will be purchasing fintech company Plaid in a $5.3 billion dollar deal.

Plaid is often called the "plumbing" behind popular peer-to peer payment apps, cryptocurrency exchanges, and mobile investing apps. They help developers share financial and banking information more easily. Venmo may be their most high-profile partners, but they also support the Cash App, Coinbase, Gemini, and Robinhood. Users of those apps probably won't recognize the name, but Plaid is well known among financial technology developers generally.

Plaid is a massive software creator: as of December, one in four people with bank accounts in the U.S. were connected to the fintech company through an app. The company drew attention by adding Mary Meeker, well known venture capitalist, to their board of directors. Plaid raised a combined $310 million from investors including $250 million from a Series C funding round in 2018. At that time, Plaid was valued at $2.65 billion. Visa is now seeking to acquire the company for twice that amount.

It has since been revealed that the investors involved in the funding the start-up included Mastercard (MA  ), Visa, Citi (C  ), and American Express (AXP  ). This means those companies would have a good idea of how Plaid was doing, and they would know what it was worth. Because the company was bought while it was still private, we won't be able to take a good look at its figure.

Visa has high hopes for this deal saying in a call with investors on Monday that it was a "long-term" play meant to set Visa up for the next decade.

"This fits well, strategically... We're excited about new businesses and the ability for this to accelerate our revenue growth over time" Visa CEO Al Kelly said of the purchase. For Visa, the purchase serves not only as the integration of another profitable company, but also as a window into the world of booming private companies shaping their future.

This could prove to be a massive win for Visa; similar API-first companies have proven to be very profitable. Twilio, another background API, has done very well as a public company. Noyo, which is similar to Plaid but deals in healthcare information and insurance APIs looks very promising; and Stripes, which occupies the same space with payments is doing well, too. Plaid is Visa's first foray into API-first technology, and it will help them prepare for similar purchases in the future.

That being said, arguably the biggest winners in this deal are the shareholders and employees of Plaid itself. Plaid's cofounders, Zach Perret and William Hockey achieved this multi billion dollar success together despite being in their early twenties when they got started in 2012.