In a slow-motion race of two retail behemoths, Amazon's trump card was its lucrative cloud-computing business.

The shuffle underscores the rivalry between the two retailers, particularly as Walmart expands its advertising and third-party marketplace businesses.

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Amazon has surpassed Walmart as the world’s largest company, measured by sales, breaking Walmart’s 13-year streak at the top of the list.

Most companies that have reached a $1 trillion market capitalization have been tech companies like Microsoft and Apple.

Amazon.com Inc. has officially dethroned Walmart Inc. as the biggest global company by revenue, a milestone attesting to the massive scale the e-commerce and cloud-computing giant has achieved since ...