Shopify posted its best quarterly revenue growth in three years on Tuesday, as healthy consumer spending and the e-commerce company’s efforts to load its platform with AI features for sellers helped drive strong holiday sales.

The Canadian company’s shares, however, were down about 2% in early trading as investors fretted over its weaker-than-expected current-quarter profit forecast.

Shopify has been investing heavily in building out AI-based tools that help its merchants with tasks ranging from image generation to inventory management, offering its ‘Shopify Magic’ suite of AI features across all subscription tiers for free.

Coupled with strong consumer spending online over the holiday season, the AI initiatives helped Shopify attract hundreds of merchants and also drove its revenue 31% higher from a year earlier to $2.81 billion in the fourth quarter, above analysts’ estimates of $2.73 billion according to data compiled by LSEG.

But Shopify’s investments into tech and expansion along with its partnership with companies such as PayPal are causing worries around margin growth. The company saw higher cloud and infrastructure hosting costs in the fourth quarter, CFO Jeff Hoffmeister said on a post-earnings call.

While the cost increase is not expected to have as much of an impact in the coming quarters, the company plans to invest heavily in research and development, marketing and into expansion in newer markets, Hoffmeister added.

Shopify expects gross profit dollars to grow at a low-twenties percentage rate in the current quarter, weaker than the 24.2% growth expected by analysts according to Visible Alpha.

“Investors may be pausing because of the profitability guidance… Shopify has been able to grow margins very substantially the last couple of years and investors want to make sure that there’s not any backsliding,” said D.A. Davidson analyst Gil Luria.

Shopify’s outlook for operating expense as a percentage of revenue to be 41% to 42% was also higher than expectations, Luria added.