Amazon shares have fallen 12% in after-hours trading as quarterly results missed Wall Street expectations, despite getting twice as much profit.
The online retailer reported annual sales over $100bn (£69.7bn), but the latest earnings left investors unimpressed.
Quarterly earnings were held back by a surge in operating expenses and slow growth in its cloud services business.
Amazon reported revenues for the fourth quarter of 2015 at $35.7bn (£24.9bn), 22% ahead of the same period in 2014 while profits more than doubled to $482m (£336m).
Profit for the year of $596m (£415m) was up from a loss of $241m (£168m) in 2014. Annual net sales rose 20% to $107bn (£75bn).
It was the third consecutive quarter that Amazon has reported a profit and the first time it has done so since 2012.
Sales for the full year were up 20% to $107bn – the first time the total has exceeded $100bn.
Before the results were released, Amazon shares had risen almost 9% on Thursday and have more than doubled in the past 12 months.
Despite the market’s pessimism, Amazon founder and chief executive Jeff Bezos was upbeat.
He said: “Twenty years ago, I was driving the packages to the post office myself and hoping we might one day afford a forklift. This year, we pass $100bn in annual sales and serve 300 million customers. And still, measured by the dynamism we see everywhere in the marketplace and by the ever-expanding opportunities we see to invent on behalf of customers, it feels every bit like day one.”
Operating expenses for the fourth quarter rose by more than a fifth to $34.6bn (£24.1bn).
Amazon also reported a 51% increase in its global Prime membership, which costs $99 a year and offers access to its video streaming service as well as free shipping.
Analysts think it has about 50 million members, but the exact number is not revealed.
Amazon has been splashing out on services for members of its $99-a-year Prime loyalty programme – or £79-a-year in the UK – including one-hour delivery and original TV programming, as it seeks to attract customers in a highly competitive marketplace.