Amazon.com Inc. on Thursday delivered the largest quarterly profit in its 20-year history, but investors apparently are thirsty for more after subsisting on thin margins for years.

The online retailer’s shares plunged as much as 15% in after-hours trading, erasing more than $30 billion in market value despite a profit that more than doubled to $482 million in the holiday period. It was also the third straight quarter of profits, the first time Amazon has done so in more than three years.

The failure to meet outsize expectations underscores the pressure Amazon now faces after teasing Wall Street in recent quarters with tighter costs and black ink. Amazon until recently put nearly every dollar it generated back into the business.

The company was one of the big growth stories among technology stocks in 2015, more than doubling its market value to over $300 billion last year and easily outperforming other tech giants like Alphabet Inc., Apple Inc. and Facebook Inc. With its $99-a-year Prime unlimited shipping program, Amazon has become a dominant force in retail and has demonstrated it can quickly gain market share in new businesses as diverse as cloud computing and hot-food delivery.

Amazon’s 22% revenue bump to $35.7 billion just missed Wall Street’s estimates, marking the sixth straight year it has come up short for this period, according to Mark Mahaney, an analyst at RBC Capital Markets.