Amazon marked its fourth consecutive quarter in which profits topped $1 billion. (Rich Pedroncelli/AP)

Amazon.com sales climbed nearly 30 percent to $56.6 billion in the third quarter, the technology giant announced Thursday, but missed expectations despite its broadly popular discount event, Prime Day.

Still, the company brought in a record $2.9 billion in profit — marking its fourth consecutive quarter in which profits topped $1 billion. The company’s stock price closed up 7 percent on Thursday, at $1,782.17, but plunged in after-hours trading to $1,668.01 a share.

“Amazon Business is adding customers rapidly, including large educational institutions, local governments and more than half of the Fortune 100,” Jeffrey P. Bezos, Amazon founder and chief executive, said in a statement. “These organizations are choosing Amazon Business because it increases transparency into business spending and streamlines purchasing, with increased control.”

(Bezos owns The Washington Post.)

In July, Amazon hit a record $2.5 billion in quarterly profit. Much of that growth was driven by Amazon Web Services, the company’s cloud-computing business, which reaped in $6.1 billion in sales. This quarter, Amazon Web Services hit $6.7 billion.

Prime Day was created four years ago and quickly boomed to become Amazon’s largest sales day of the year. The bonanza brings in billions in sales for the company but was dogged by website glitches and worker strikes this year. Nearly 1,800 Amazon workers in Spain went on strike that day, joining a chorus of thousands of other workers calling for better conditions, pay and health benefits. The labor protests mounted scrutiny of the company’s hiring and labor practices as Amazon looked to add thousands of warehouse jobs to keep pace with its massive growth.

Amazon’s Prime membership program, for which users pay $119 a year, has more than 100 million members worldwide. Though Amazon has largely kept specific metrics on the program under wraps, some have raised the possibility that the Prime member count may be reaching a saturation point as there are fewer and fewer Americans left to reach.

Also on Prime Day, which was July 16, the sale compromised Amazon’s website almost immediately. Amazon’s site and mobile app crashed for about 45 minutes, leaving customers with a message that read: “UH-OH. Something went wrong on our end.”

Charlie O’Shea, Moody’s lead retail analyst, noted that Amazon’s third-party sales growth of 31 percent reflects ongoing “attractiveness of Amazon’s services and capabilities to other retailers.”

Cooper Smith, head of Amazon research at Gartner L2, a firm that benchmarks brands' digital performance, noted that before Thursday, Amazon had posted two consecutive quarters of triple-digit growth in advertising. Amazon’s breakneck advertising expansion, just behind Google and Facebook, poised the company to report strong third-quarter earnings — especially when combined with the boon from Prime Day.

“We see Q3 as a standout quarter for Amazon and for product sales, largely because of Prime Day,” Smith said.

Smith said it remained to be seen how Amazon would tackle its international growth, particularly in markets it is just beginning to enter, like Brazil. Any concerted international efforts would clarify Amazon’s plans to compete with the likes of Walmart, for example, which bought a 77 percent controlling stake in the Indian retailer Flipkart for $16 billion earlier this year — snapping up 100 million customers in one transaction.

Bob Phibbs, chief executive of New York-based consultancy the Retail Doctor, said Amazon’s earnings make clear the company’s reliance on Amazon Web Services. Even with high analyst expectations, Phibbs said, “it all comes down to one thing — whether their e-commerce business can actually make money.”

Still, Amazon has also shown a willingness to invest in bricks-and-mortar stores — including through Amazon Go locations and New York’s new Amazon 4 Star store, Phibbs said.

“Ultimately,” he said, “they are starting to understand that you can make money when people talk to a human being instead of clicking a button.”

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