Microsoft delivered one of its strongest quarters on record. Investors still weren’t impressed.

After the closing bell on Wednesday, Microsoft (MSFT) reported a blockbuster second quarter that beat Wall Street expectations on both earnings and revenue, with cloud sales topping $50 billion for the first time in the company’s history. Yet despite the standout performance, Microsoft’s stock slid 6% before Thursday’s open, underscoring growing investor anxiety over the soaring cost of the AI boom.

Microsoft posted earnings per share of $5.16 on revenue of $81.27 billion, comfortably ahead of analysts’ forecasts of $3.92 EPS and $80.3 billion in revenue. The results reinforced Microsoft’s position as one of the biggest winners of the global artificial intelligence arms race.

At the heart of the quarter was Microsoft Cloud, which generated $51.5 billion, edging past expectations and soaring from $40.9 billion a year ago. It marked a symbolic milestone for the company—and a clear signal that AI-driven cloud demand remains red-hot.

“We are only at the beginning phases of AI diffusion,” CEO Satya Nadella said in a statement. “Already Microsoft has built an AI business that is larger than some of our biggest franchises.”

Microsoft’s Intelligent Cloud segment, which includes Azure, delivered $32.9 billion in revenue, beating Wall Street estimates. Meanwhile, Productivity and Business Processes, powered by Microsoft 365 commercial and consumer cloud offerings, reached $34.1 billion, topping expectations as businesses continue to embed AI into everyday workflows.

One of the most closely watched AI indicators—remaining performance obligations (RPO)—jumped to an eye-popping $625 billion, with 45% tied to OpenAI commitments. The metric has become a crucial barometer for future AI demand, and it suggests Microsoft’s backlog is swelling fast.

Despite the strong demand, Microsoft is running into a familiar problem: it can’t build AI infrastructure fast enough.

The company acknowledged ongoing AI capacity constraints, meaning customer appetite for AI services is currently outpacing Microsoft’s ability to deliver. To close the gap, Microsoft is spending aggressively. Capital expenditures surged to $37.5 billion in the quarter, up sharply from $22.6 billion a year earlier.

That massive spending spree appears to be rattling investors, many of whom are increasingly skeptical about how quickly AI investments will translate into profits.

Microsoft’s More Personal Computing segment—covering Windows, Surface devices, and Xbox—generated $14.3 billion, landing right in line with expectations. While not flashy, the unit provided stability amid the company’s rapid AI expansion.

Microsoft’s stock is now up just 7% over the past 12 months, slightly ahead of Amazon’s 2% gain—but dramatically trailing Google’s stunning 69% surge. Much of Google’s momentum has been fueled by the launch of Gemini 3, which has reshaped the AI landscape and positioned Google ahead of Microsoft’s partner, OpenAI, in the race for model leadership.

Microsoft briefly crossed a $4 trillion market capitalization earlier this year, thanks to enthusiasm around its OpenAI partnership. But as AI costs balloon and competition intensifies, investors appear less willing to reward scale alone.

Microsoft’s quarter proved one thing beyond doubt: AI demand is real, massive, and accelerating. But the market’s reaction highlights a deeper concern—how much it will cost to stay ahead, and whether returns will come soon enough.

For now, Microsoft is pushing the frontier of AI faster than almost anyone. Whether Wall Street regains confidence may depend less on how big the numbers get—and more on how efficiently the company can turn its AI empire into sustained profit.