Amazon Cloud needs to deliver after Microsoft, Alphabet miss estimates

Amazon.com Inc. shares have largely climbed on the back of two trends: strength in its cloud business and a focus on costs. Now both could be in question.

Disappointing results from major cloud-computing companies Alphabet Inc. and Microsoft Corp. suggest reasons to be cautious about Amazon Web Services, the biggest player in the space — and a central plank in Wall Street’s nearly unanimously positive view on the stock. At the same time, a trend of growing capital expenditures as firms invest heavily in artificial intelligence could, if Amazon follows suit, force a recalibration of how profitable it can be this year.