San Francisco-based Instacart raised $400 million in its latest financing round in March, boosting the company’s valuation to $3.4 billion as investors showed more enthusiasm for a business model whose viability had long been in question.

Some have noted Instacart’s resemblance to the dot-com-era grocery delivery company Webvan, which raised $800 million and went public but then went bankrupt.

“(IPO) is not even an internal discussion at this point,” Instacart co-founder Max Mullen told Reuters at the Collision tech conference in New Orleans. “We recently raised a sizeable (financing) round so we are focused on spending that money carefully, responsibly, and wisely.”

Instacart is backed by prominent venture capital firms such as Sequoia Capital, Khosla Ventures, Kleiner Perkins Caufield & Byers, and Thrive Capital.

The company operates in 45 U.S. markets including San Francisco, Chicago and New York, and plans to add 40 markets in the next quarter.

“We are going to double the markets (we are in) in the next quarter and drastically increase coverage of Instacart. Overall, we plan to make the service available to 80% of U.S. households by 2018,” Mullen said.

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Instacart has deals with about 140 retailers including Whole Foods (WFM), Costco (COST), Target (TGT), and Safeway (SWY) to deliver groceries to consumers. Customers can order from those stores through the Instacart app, and an Instacart driver delivers the food in as little as an hour.

Although Instacart does not disclose revenue, Mullen said the company has been gross margin profitable in the majority of its markets since fall 2016.

Instacart also launched advertising for consumer packaged good companies including Pepsi (PEP), Unilever (UL), and General Mills (GIS) on its website about 18 months ago, which has become a big portion of revenue.

“Advertising is the fastest-growing part of our revenue. It’s the difference between being profitable and not being profitable,” Mullen said.