Amazon shares fell 4% in Frankfurt on Friday a day after the retailer's results showed weakness in its cloud computing unit and it forecast and lower-than-expected first-quarter revenue and profit.

The pressure is on Amazon.com to deliver on lofty expectations for cloud computing in its fourth-quarter results on Thursday.

Amazon.com Inc. shares have largely climbed on the back of two trends: strength in its cloud business and a focus on costs. Now both could be in question.

Amazon.com topped Wall Street estimates for quarterly revenue on Thursday, as strong sales over the holiday shopping season boosted its retail business, helping offset weakness in the cloud computing unit.