Slice, a startup that helps independent pizzerias build an online business, has raised another $40 million in Series D funding.

The round was led by Cross Creek, with participation from KKR, GGV Capital and Primary Ventures, as well as Twitter’s former CEO Dick Costolo and former COO Adam Bain (through their firm 01 Advisors).

Last spring, the startup announced a $43 million Series C. Why not raise more money this time? Founder and CEO Ilir Sela described this as “a quick round” to get Costolo and Bain  on-board as investors. He also suggested there may be additional fundraising conversations in the not-too-distant future.

“Slice has emerged as the leader in powering these types of small businesses that have been serving our communities for decades,” Bain said in a statement. “We look forward to working with Ilir and the incredible team at Slice to marry our significant operating and business-scaling experience with Slice’s focus on enabling economic growth in this category.”

Slice has built a mobile app and website for ordering from local pizzerias, but it also provides tools so they can build their own websites, run marketing campaigns, improve their search engine optimization and more. Slice only charges those pizzerias a fixed $2.25 per order, and last fall it even removed the fee for orders under $10.

The company continues to expand its products and services with the recent launch of a point-of-sale system for pizzerias called Slice Register, as well as a cross-pizzeria loyalty program called Slice Rewards.

Some of this might sound a bit niche — a POS system, just for pizzerias? — but when I brought this up with Sela, he replied, “I love it when people say that, because then they continue to stay out of the way.”

Slice already has 15,000 pizzerias on the platform, with plans to increase that number to 20,000 at the end of the year. He added that although the current addressable market consists of 57,000 independent and small chain U.S. shops, with the Slice Accelerate program (where the startup provides select pizzerias with $15,000 worth of technology and services) “there could be 100,000 in the U.S.”

“With Accelerate, we’re taking inefficient pizza shops who are predominantly offline and helping them realize their vision for their brand,” he continued. That might mean improving an existing location, or it might mean launching new ones. In fact, he said the new program has already helped to revamp Pizza Mia in Staten Island and will work with Crown Heights-based Billy’s Pizza & Pasta to open a second location.

“I definitely think that long term, there’s a big question whether our very unique model could be applied to other verticals,” he said. “I think it can, but it would be a mistake to move into those verticals today, because of the opportunity that it exists in pizza.