Executives from Microsoft and Google, Amazon's two top rivals in the cloud business, both hit on a key theme in their presentations at a financial event on Tuesday: They're not going to compete with their own customers.

The notion isn't theoretical. As Amazon has grown and expanded, it has introduced products that can be used as an alternative to what some of its own business partners offer.

And after Amazon went beyond its traditional role of e-commerce heavyweight and became more active in brick-and-mortar retail through its Whole Foods acquisition, some other retailers, like Albertsons and Walgreens, have announced cloud deals with Microsoft.

Executives at Google and Microsoft have previously said that they don't aim to become competitive with the companies that give them revenue. But at the Goldman Sachs Technology and Internet Conference in San Francisco, representatives from both companies emphasized that point.

"I'll tell you what I'm seeing and see if that answers your question, perhaps is, I would say things like retailers and financial services companies now and, now into health care — seeing Amazon go into those businesses and saying, 'Gosh, am I going to give money to people who are now competing with me?'" Julia White, corporate vice president of marketing for Microsoft's Azure cloud, said in response to one audience member's question.

Data is a bigger issue -- businesses probably don't want to share it with a competitor, which is why companies like Kroger, Walgreens and Gap are moving to Microsoft Azure, White said.

"We're not going to turn around and compete with our customers. And that's obviously a big, big theme that we hear about of the market as well in terms of overall trusting Microsoft as a partner," she said.

Thomas Kurian, the new CEO of Alphabet's Google Cloud business, also touched on the subject in his inaugural pitch on Tuesday.

"Google is very clear that we're here to enable partners, we're not here to compete with partners," Kurian said. In his presentation he pointed to several retail customers, including Best Buy, Home Depot, Metro Group and Target.

AWS does have retail customers, as well as financial services and health care customers. The company has previously said that "there are times when there is some degree of overlap with what our customers offer, but most of these market segments are quite large and support several successful entries."

But now Google and Microsoft are both actively focusing on key sectors where Amazon is active — not just retail, but also health care, following Amazon's acquisition of online pharmacy PillPack and its health venture with Berkshire Hathaway and J.P. Morgan Chase.

"The partner meetings I had this morning were like, 'Hey, I used to work with AWS, but now I don't. I worry they're competing with me,'" White said.

Watch: AWS CEO Andy Jassy talks competition and innovation