Amazon offered a cautious sales outlook for the current fourth quarter that encompasses the critical holiday shopping period after delivering fiscal third-quarter results that came in below Wall Street analysts’ expectations.

The Seattle-based tech giant, however, posted strong sales growth in its prominent cloud computing unit. Sales in its so-called Amazon Web Services rose 39.3% to $46 billion during the latest quarter ended Sept. 30, higher than the 37% clip in the previous quarter. It marked the fastest growth rate in nearly five years, the company said.

Still, shares were down 7% in after-market trading when the results were released as investors focused on its core operations and worried about Amazon’s burning through cash as it invests heavily in artificial intelligence .

Investors have been closely watching Amazon’s quarterly earnings to see if the company’s big spending on artificial intelligence is starting to pay off.

Amazon’s CEO Andy Jassy told investors on the call Thursday that he still…