Walmart's e-commerce business achieved profitability largely through the success of its delivery services and its other streams of income such as its marketplace e-commerce platform and advertising, a company executive said recently.

John David Rainey, Walmart Inc.'s chief financial officer, said he views the company's first-quarter 20% growth in e-commerce across all its segments as sustainable, with customers willing to pay for faster delivery.

Rainey made the remarks in a June 9 call at Oppenheimer & Co.'s annual consumer growth and e-commerce conference. The global financial institution refers to these one-on-one interviews as "fireside chats."

Rupesh D. Parikh, Oppenheimer's managing director and senior analyst who covers food, grocery and consumer products, conducted the interview.

In introducing Rainey, Parikh said Oppenheimer is "very upbeat toward (Walmart's) prospects, including the potential for outsized profit growth to continue in the coming years."

Rainey said Walmart's "got a lot of good momentum."

"In the last year, we've almost doubled from the first quarter of last year the number of deliveries in under three hours," Rainey said. He said they were up about 90%.

"We continue to see that customers are willing to actually pay for that expedited delivery," he said.

The Bentonville-based retailer has had some weeks recently in which about 40% of its deliveries were express delivery, Rainey said.

"In the last quarter, fully one-third of our overall deliveries were this express delivery," he said. "And that has really helped drive some of the economics of our e-commerce business."

Speed and convenience matter to everyone regardless of their income level, Rainey said.

Parikh said that from his visits to remodeled stores across the country, he thinks those hold "significant longer-term potential" on the general merchandise front.

But he asked Rainey what he saw as the bigger opportunities to drive share gains over time.

"And then within general merchandise, are there any particular categories where you see bigger opportunities at this juncture?" Parikh asked.

Rainey said improving the in-store experience has focused on fashion and home categories, and the retailer continues to expand its brand assortment.

"But marketplace" the online market that hosts third-party sellers along with Walmart products "is something that certainly stands out to me as a big opportunity for us with general merchandise as well," Rainey said.

"And so we'll continue to focus on that because it unlocks other opportunities like advertising, Walmart fulfillment services, things like that, which are all accretive to our bottom line," Rainey said.

Parikh said the results were impressive, but asked what Walmart is seeing on the competitive promotional front in the U.S.

Rainey described it "as a pretty rational environment right now."

The company has said in previous quarters that it didn't like its price gaps or where they stood compared to other retailers, Rainey said.

"And so we invested into some of that, both in our club format at Sam's as well as at Walmart in specific geographies," Rainey said, "and we feel much better about how we're positioned there right now."

"We want to continue to be known for value as well as convenience for customers," Rainey said. "So we'll need to play offense there."

"We want to continue to be that price leader for customers," he said.