Microsoft will report earnings on Wednesday, 28 October, and once again this will be one of those times where the numbers themselves might not be the biggest story.Now, don't get me wrong. The results will still matter. Analysts are expecting revenue of around $90.6 billion, up nearly 17% from a year ago, alongside EPS of $4.71. Those are strong growth numbers, especially when you consider just how big Microsoft already is.But as has been the case with most big tech earnings, investors will be paying much closer attention to what management has to say about Microsoft's AI ambitions more than anything else. And that will particularly be the case after the recent selloff in tech stocks over the past two weeks.Microsoft is already spending an extraordinary amount of money to build out its AI infrastructure. The firm's capital expenditure, including finance leases, hit roughly $41 billion in the previous quarter and management expects that figure to exceed $50 billion this quarter. Just think about that for a moment. We're talking about more than $50 billion in spending over three months alone.Of course, Microsoft has good reasons to be investing so aggressively. Azure revenue grew 43% year-on-year in the previous quarter, with management guiding for roughly 45% growth in constant currency this quarter. Besides, the underlying backdrop signals that demand remains strong enough that available computing capacity is still struggling to keep up. As such, I don't think anyone is seriously questioning the notion of whether businesses want more AI computing power. The demand is clearly there.Instead, the main concern is how much Microsoft has to keep spending to satisfy that demand and whether the returns will eventually justify the investment.The fact of the matter is that building data centres and buying advanced chips isn't cheap. And while those investments can support years of growth down the line at some point in the future, they also come with substantial costs that investors cannot simply ignore forever at the present time.As the market focus continues to revolve around that now, I would be closely watching Azure's growth outlook, cloud margins and any changes to Microsoft's capital expenditure plans this week. And considering how sensitive the tech sector has been in recent weeks, the implications could stretch well beyond Microsoft.If Azure growth continues to impress and investors get greater confidence over future returns, that could help calm some of the nerves surrounding the broader AI trade. In particular, semiconductor companies and data centre operators would certainly welcome that reassurance.But if spending keeps accelerating while profit margins struggle to keep up, investors will once again start questioning the economics of the AI boom more aggressively.I don't think anyone is doubting Microsoft's capacity to once again deliver another strong quarter. The company has given investors plenty of reasons to expect one and amid the lofty expectations among big tech, posting blockbuster earnings these days seem to be the norm.The only issue now that I'm seeing is that strong earnings alone may not be enough to appease investors. The market already knows that AI demand is booming. And so the focus has now clearly shifted to looking for evidence that all the money being spent to capture that demand will eventually pay off. And Microsoft's earnings will be another test of that very shift in sentiment. This article was written by Justin Low at investinglive.com.