Shares of e-commerce and cloud-computing giant (AMZN -0.17%) are getting a lift Friday morning, rising nearly 3% as of 10:15 a.m. EDT. The stock's boost follows news that Warren Buffett's Berkshire Hathaway (BRK.B 0.38%) (BRK.A 0.58%) has been buying shares of the company. Berkshire's impressive long-term investment track record and the conglomerate's focus on value often mean any stock the company invests in receives reinvigorated interest from the Street.

The investment in Amazon follows a strong first quarter from the company, bolstered by earnings per share that obliterated analysts' estimates.

Boxes in an Amazon fulfillment center

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It's not Buffett buying

While Berkshire is buying Amazon stock, it's not the Oracle of Omaha buying shares, the CEO and chairman of Berkshire clarified in an interview with CNBC.

"I'll tell you one thing you'll see in the 13-F, which comes out in a couple weeks. ... One of the fellows in the office that manage money...bought some Amazon," Buffett said, referring to one of two of his investment lieutenants, Todd Combs and Ted Weschler, each of whom manages more than $13 billion.

Acknowledging he has been impressed by the company for a long time, Buffett added, "Yeah, I've been a fan, and I've been an idiot for not buying it. But I just want you to know it's no personality changes taking place."

Investors will have to wait until Berkshire's latest 13-F filing to see exactly how much Amazon stock the company bought. But given the amount of money Buffett's Combs and Weschler manage, the investment isn't likely to compare very well to some of Berkshire's biggest holdings, like its $53 billion stake in Apple or $28 billion stake in Bank of America, for example.

However, it's worth noting that Combs and Weschler's investments have helped spark Buffett's interest before. This was the case with Berkshire's initial investment in Apple, which was first made by one of these two managers before Buffett started loading up on the stock until it became Berkshire's largest holding.

Momentum at Amazon

Meanwhile, Amazon is seeing extraordinary momentum, especially on its bottom line.

In its first quarter of 2019, Amazon reported $59.7 billion in revenue, up 17% year over year. This helped the company register net income of $3.6 billion during the quarter, up from $1.6 billion in the year-ago quarter. On a per-share basis, profits were $7.09 per share, up from $3.27 in the year-ago quarter and crushing analysts' average forecast for earnings per share of $4.72.

The company has been benefiting from economies of scale; its e-commerce and cloud-computing sales continue surging despite already being in unprecedented territory. Amazon's trailing-12-month operating margin has swelled from 2.3% at the end of 2017 to 6.2% today.