Amazon Web Services is not only helping Amazon generate billions of dollars in revenue, but also — perhaps more importantly, to Wall Street at least — a crucial chunk of the company’s operating income.

Amazon will report its fourth quarter earnings after today’s closing bell and if the historic trend above is any indication, AWS should continue to see growth both with net sales and operating income.

Today’s results will provide the first detailed glimpse of how Amazon fared during the peak holiday shopping season. Overall, analysts expect the company to post revenue of $44.68 billion for the December quarter, up from $35.7 billion a year earlier, with earnings of $1.35/share, up from $1/share last year.

AWS, Amazon’s cloud computing business, brought in $3.2 billion in revenue last quarter, which accounted for nearly 10 percent of Amazon’s company-wide quarterly revenue of $32.7 billion. That was up from $2.9 billion the previous quarter, which was up from $2.6 billion the quarter before that.

AWS accounts for an increasingly large percentage of Amazon’s net sales, nearly doubling in Q3 from the 4.8 percent it represented less than two years ago.

Unlike many of Amazon’s other arms, AWS also generates a healthy profit. AWS’s operating income in Q3 — $861 million — was 150 percent of Amazon’s operating income as a whole, helping offset a $541 million operating loss in the company’s international segment.

Amazon has come to depend on Amazon Web Services to fuel the rest of its sprawling business and feed its global ambitions. It’s impossible to say how Amazon would be managing its expenses and profit margins if it hadn’t launched AWS more than a decade ago. But it’s clear that AWS has emerged as a huge economic engine.

AWS, used by Amazon itself and customers like Netflix, competes with other cloud computing products from companies like Google and Microsoft.

The Guardian published a solid piece today that details the history of AWS and how it’s become so important for Amazon’s overall business.

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