Amazon (NASDAQ:AMZN) investors likely know the company's most visible business -- e-commerce operations -- isn't its most profitable. Instead, the company's smaller cloud business, Amazon Web Services (AWS), is its most profitable on account of higher margins. Last fiscal year, AWS produced 105% of Amazon's operating income as losses in international retailing offset North American retailing profit.

Therefore, it's key for investors to pay close attention to Amazon's market position in cloud computing. Increasingly, the cloud has become a more-competitive industry, with second-largest provider Microsoft (NASDAQ:MSFT) starting to pick up market share. Do Amazon investors have anything to fear?

Cloud computing concept. Network of connections in shape of cloud.

Image Source: Getty Images.

Gartner found Microsoft is gaining on Amazon

Per Gartner, the worldwide public infrastructure-as-a-service industry continues to post torrid growth rates, as spending increased 29.5% in 2017, growing from $18.2 billion to $23.5 billion. No surprise that Amazon continues to significantly lead this industry with a 51.8% market share. However, Amazon's lead over its peers continues to narrow, as the company lost 1.9 percentage points of share this year.

Company 2017 Revenue 2017 Market Share 2016 Revenue 2016 Market Share 2017-2016 Growth 
Amazon $12,221 51.8% $9,775 53.7% 25%
Microsoft $3,130 13.3% $1,579 8.7% 98.2%
Alibaba $1,091 4.6% $670 3.7% 62.7%
Google $780 3.3% $500 2.7% 56%
IBM $457 1.9% $297 1.6% 53.9%
Others $5,902 25% $5,392 29.6% 9.5%
Total $23,580 100% $18,213 100% 29.5%

Data from Gartner and in millions. 

The biggest named gainer in Gartner's data was Microsoft and its Azure product. The company grew total market share from 8.7% in 2016 to 13.3% last year on the back of 98.2% growth. Overall, the cloud industry appears to be moving further toward a consolidation phase, as the top five vendors now claim 75% market share versus 70.5% in 2016.

These figures are for infrastructure as a service (IaaS), the base layer of the cloud stack. During the last conference call, CEO Satya Nadella noted the company's commercial cloud business exceeded $23 billion, but this comparison includes revenue attributable to Office 365, its cloud-based software-as-a-service product.

Two reasons for Azure's rapid growth

Azure's revenue growth has been greatly aided by large retailers with significant cloud-based spending: Walmart, Target, Costco, and Walgreens have all decided to use Microsoft's off-site servers, storage, and networking services. This has nothing to do with quality, but rather retailers have complained Amazon uses high-margin AWS to offset razor-thin margins from its e-commerce business. Former Walmart CEO Bill Simon went further, calling Amazon's strategy of using AWS to backstop low e-commerce profits "anti-competitive."

Additionally, Microsoft has done an admirable job building down the cloud stack with its platform-as-a-service (PaaS) and software-as-a-service (SaaS) offerings versus Amazon's IaaS-heavy approach. As noted earlier, the company has successfully transitioned its Office product to the cloud, with Office 365 revenue now eclipsing traditional Office licensing.

Growth rates can be deceiving

More recently, there's been an increase of headlines declaring that Microsoft is growing much faster than Amazon in the cloud. While this is certainly true, it's an incomplete picture due to the tremendous difference in growth rates. Revisiting the table above, Microsoft grew IaaS-attributable revenue 98%, which is admirable, but still only increased the figure by $1.6 billion.

Because Amazon continues to dominate this industry, it's difficult for the company to grow much more than the industry growth rate because of its disproportional pull on the total growth rate. Perhaps a better way is to look at this as a percentage of total growth. Amazon is still responsible for 45.6% of revenue growth in the cloud. Although the company would prefer to grow market share, it's clear it is still the biggest player in the market and not hemorrhaging market share.

  2017 2016 Growth (YOY)  % of Industry Growth
Amazon $12.2 $9.8 $2.4 45.6%
Microsoft $3.1 $1.6 $1.5 28.9%
Total  $23.6 $18.2 $5.4 100%

Data from Gartner and in billions. Figures may not exactly match growth percentages due to rounding.

Although Amazon should be less comfortable with its formidable position of a few years ago, Microsoft has been greatly aided by those large retailers, and it's likely IaaS-related revenue growth will slow in the upcoming years. Ultimately, however, cloud will not be a winner-take-all market, as the consolidating industry is expected to increase 58% over the next two years. In the end, investors in both companies should be encouraged by Gartner's report.

This article represents the opinion of the writer, who may disagree with the “official” recommendation position of a Motley Fool premium advisory service. We’re motley! Questioning an investing thesis -- even one of our own -- helps us all think critically about investing and make decisions that help us become smarter, happier, and richer.