What happened

Shares of StoneCo (NASDAQ:STNE) traded up 10% on Friday morning after the Brazilian financial tech company reported strong third-quarter results that showed rapid growth in its home market. Warren Buffett's Berkshire Hathaway bought into StoneCo last year, and it has to be pleased with the company's progress.

So what

StoneCo after markets closed Thursday reported third-quarter adjusted net income of 201.9 million reals ($48.2 million) on revenue of 671.1 million reals ($160 million), up 126% and 62%, respectively, year over year. The company's adjusted net margin grew to 30%, up 8.5 basis points from a year prior, and total payment volume rose 50% year over year to 32.6 billion reals ($7.79 billion).

A handheld credit card processing machine.

Image source: Getty Images.

The company ended the quarter with 428,900 total active clients, up 83% from 2018, thanks to the addition of 68,700 new clients during the quarter.

CEO Thiago Piau in a letter to shareholders discussing the results said that despite the growth, the company is still in its early stages.

"I remain very excited to continue to implement our vision of becoming more present in our merchants' daily activities, helping them to manage their businesses more effectively, become more productive and grow faster," Piau said.

Now what

Brazil's payment industry is rapidly evolving, and StoneCo based on its results is well positioned to be one of the primary beneficiaries of that evolution. That's going to require more resources and higher expenses, with administrative costs up 14% year over year and selling expenses up 103%. But so far StoneCo is generating growth that more than justifies those added costs, and admin costs as a percent of revenue actually dropped more than 400 basis points from the third quarter of 2018.

These are early days for StoneCo, and a lot could still go wrong. But all investors, Warren Buffett included, should be pleased with the third quarter the company just completed.