Amazon had a heck of a holiday. The online retail giant posted Q4 earnings today, reporting $72.4 billion in revenue, topping last year’s $60.45 billion and besting the analysts’ forecast of $71.92 billion.

Extremely wealthy individual Jeff Bezos singled out Alexa’s record holiday season as a source of the robust quarter.

“Alexa was very busy during her holiday season. Echo Dot was the best-selling item across all products on Amazon globally, and customers purchased millions more devices from the Echo family compared to last year,” the CEO said of the earnings. “The number of research scientists working on Alexa has more than doubled in the past year, and the results of the team’s hard work are clear.”

Amazon Web Services also played a key role here, with a massive $2.2 billion operating income. AWS’s $7.43 billion sales beat the $7.29 billion analysts’ estimate and marked a healthy jump from last year’s $5.11 billion.

The numbers look good, though; as CNBC notes, the 19.7 percent revenue growth for the quarter is the lowest since 2015. Wall Street reaction was further dampened by Amazon’s lowered guidance for Q1. Amazon put revenue for the upcoming quarter at between $56 billion and $60 billion, below analyst expectations of $60.99 billion.