Christa Quarles has a lot on her plate. The Carnegie Mellon University alumna is CEO of OpenTable, the largest online restaurant reservation service that enables diners to make reservations using a computer or smartphone app.

For a monthly rate and a fee for every seat filled, more than 40,000 restaurants around the world participate. It’s money well spent. OpenTable averages 21 million restaurant reservations monthly, including at Pittsburgh’s Joseph Tambellini restaurant.

“It gives you exposure you wouldn’t get, especially for business travelers. It more than pays for itself,” according to the restaurant’s owner, Joseph Tambellini, who estimates that one third of his customers are booked through OpenTable.

On a recent Friday, another Pittsburgh-based restaurant, Nakama, served an additional party of six because of OpenTable. It was the 23rd birthday of Debra Moskat’s son, but his friends had decided at the last minute that they would celebrate with him on Saturday, which meant he had no plans on his actual birthday. Moskat opened the OpenTable app on her phone and clicked the “dinner tonight” category.

“I scrolled down and came across Nakama, where I’d eaten before and had been entertained by the chefs who flamboyantly prepare the meal right at the table,” Moskat said.

From there, she clicked on an available 7:30 p.m. reservation, received an email confirmation, followed by a reminder later in the day. When she and her family arrived at the Japanese steakhouse, their table was ready.

“Good thing, too,” she joked, “because my husband can get hangry.”

OpenTable goes far beyond Pittsburgh. Quarles travels the world to grow the dining network. In her San Francisco headquarters, she and her team develop algorithms to personalize the diner’s search results based on factors such as personal favorites, proximity and popularity. The algorithms sift through reams of data to tailor suggestions.

“Data is everything. My ability to handle stats and appreciate data and information was honed at CMU,” said Quarles, who majored in economics and German and earned her CMU undergraduate degree in 1995.

She credits her German major for preparing her to embrace other cultures around the globe. In fact, her German professors pushed her to study economics at the University of Vienna, even though it meant missing part of her basketball season for the Tartans.

After completing her demanding undergraduate workload at CMU, she secured an MBA at Harvard. “I always joke that CMU made Harvard seem easy,” she said.

After her schooling, Quarles became a partner of equity research at Thomas Weisel Partners for nine years. She also worked with The Walt Disney Company, becoming senior vice president and general manager of mobile and social games. Next, she became chief business officer at Nextdoor. She joined OpenTable in 2015, and was quickly promoted to CEO of the company that now has nearly 1,000 employees. In 2014 it was bought by The Priceline Group, the world’s largest online travel company.

Though OpenTable was one of the first online apps meant for the dining space, it has plenty of competitors. One of them is Nowait, a CMU startup that lets diners use their mobile phones to add themselves to a virtual wait list. Nowait recently partnered with Yelp, which, among its services, publishes crowd-sourced restaurant reviews. Despite Nowait and other startups, Quarles said, “Our biggest competitor is the phone.”

To remain at the forefront, she points out that OpenTable offers more than restaurant booking. Users can read reviews and earn points that can be redeemed for free meals. In addition, through a pilot program in Boston, OpenTable is testing a perk that enables diners to use points they accumulate for help in getting a table at trendy restaurants.

“It’s a real opportunity for active diners to get hard-to-get reservations,” Quarles explained.

With her travel schedule and visits to member restaurants, Quarles rarely cooks at home. She’s not alone. Americans spend more money on restaurant food than they do on the food in their refrigerators. That leaves plenty of room for growth in the online restaurant reservation space, predicts Quarles.