Amazon Cloud Sales in Focus After Microsoft’s $500 Billion Rout

All eyes will be on Amazon.com Inc.’s cloud business when the technology giant reports earnings on Thursday, after shares of Microsoft Corp. plunged last week due in part to slowing growth at its key cloud-computing platform.

This was not an issue for Amazon’s October earnings, as its shares jumped almost 10% following better than expected revenue from Amazon Web Services, also known as AWS. Now, however, fear is rippling through the tech sector, and Amazon investors are increasingly concerned that the slowdown at Microsoft’s Azure indicates broader weakness for cloud providers. Microsoft shares are down more than 16% since the report on Jan. 28, erasing roughly $500 billion in market value.