Amazon.com briefly became the world’s most valuable company Monday.
The online retailer surged 5.2 percent at its highs, pushing its market capitalization past $870 billion.
That briefly topped Microsoft for the most in the world, a title the software maker stripped from Apple last week for the first time in 8 years.
Apple and Microsoft have one of the most storied rivalries in Silicon Valley, one that goes back to the mid-1970s, when both were founded within a year of each other and focused on making breakthroughs in developing personal computers.
Microsoft dominated in the dot-com era but subsequently lost ground as the Cupertino, California-based Apple launched such iconic products as the iPod and especially the iPhone, which would grow to become its most important product line.
Yet now, that very product is among the the challenges facing Apple, with concerns over weak iPhone demand pressuring shares to fall 25 percent from record levels.
Microsoft isn’t immune to weakness in the technology sector, although the Redmond, Washington-based company has held up much better, falling about 8 percent from its own all-time high in October as investors take to its enterprise-oriented business, as well as the success of its cloud-computing division.