Amazon, the world’s largest company by market capitalisation, reported improved earnings and profits late on Thursday.

The company reported its third record profit in a row, capitalizing on a strong holiday retail season and its growing, high-margin businesses such as cloud computing and advertising.

The Seattle-based company reported a profit of $3.03bn, or $6.04 a share, up from $1.86bn, or $3.75 a share, on the same quarter a year earlier. Revenue grew 20% to $72.38bn.

Amazon’s voice-controlled virtual assistant Alexa, and the devices which play it, helped the performance. “Alexa was very busy during her holiday season. Echo Dot was the best-selling item across all products on Amazon globally, and customers purchased millions more devices from the Echo family compared to last year,” Jeff Bezos, Amazon founder and CEO, said in a statement.

Most importantly for investors, Amazon’s cloud-computing division said revenue jumped 45% in the fourth quarter, cementing its lead over Google and Microsoft.

The division has been growing at 40% per annum and is a high margin business compared to retail. The cloud business has become crucial to the success of its parent, not only for revenue but also for profits.

Sales at Amazon Web Services climbed to $7.43bn from $5.11bn a year ago, topping the $7.29bn estimated by analysts. The segment makes up around 10% of total revenue.

Amazon stock is up 18% over the past year. Its market cap, more than $840bn as of Thursday afternoon, is the largest of any publicly traded company in the world.

Amazon stock fell almost 50 points from its closing price of $1,718 on fears of reduced margins from sales in India and increased shipping costs in the US.