Nu Holdings (NU) reported its first-quarter results after the bell on Thursday, and on paper, they looked pretty good. Revenue came in at $5.32 billion, up 42% from a year ago and ahead of the Street's $5.04 billion estimate. It was the first time the company crossed the $5 billion quarterly revenue mark.

Net interest income hit a record $3.25 billion, up 12% from the previous quarter. Net income was $871 million, a 41% jump year-over-year. The company also added about 4 million customers in the quarter, bringing its global total to over 135 million. In Brazil, it now has more than 115 million customers, making it the largest private financial institution there. In Mexico, it's the third largest with over 15 million customers, and in Colombia, it's approaching 5 million.

So why is the stock getting slammed? Shares were down 9.51% in after-hours trading to $11.70, dipping below their 52-week low of $11.71. The 52-week range is $11.71 to $18.98.

The market seems to be focusing on a few things that could be overshadowing the headline numbers. Margins, slower-than-expected customer growth, and increased spending on a new region are likely weighing on sentiment.

CEO David Vélez emphasized the company's AI transformation as a core priority. "We are not adding AI to banking, we are rebuilding banking around AI," he said. He noted that over 15 million monthly active users are using the company's AI Private Banker functions.

After successfully launching in Brazil, Mexico, and Colombia, Nu is now eyeing the U.S. market with a "disciplined expansion." The company said it will test the long-term opportunity in the U.S. while protecting its core business, ensuring that maximum investment stays below certain levels in 2026 and 2027. But any new market expansion comes with costs, and investors might be worried about the near-term impact on profitability.

So while the quarter itself was strong, the market is looking ahead and seeing potential headwinds. For now, Nu's stock is feeling the pressure.