Walmart posted its biggest earnings surprise in 31 years Tuesday as shoppers rushed in to spend their stimulus checks, and online sales nearly doubled during the coronavirus pandemic.

The discount retailer has been leveraging its massive store base and the investments it’s made in e-commerce to supply customers with food and other goods during the pandemic. U.S. same-store sales climbed 9.3% in the fiscal second quarter, while U.S. e-commerce sales surged 97%, as more customers shipped packages to their homes and used same-day delivery and curbside pickup.

Shares were down less than 1% in premarket trading after jumping by more than 6% at one point to reach an all-time high. 

Here’s what the company did in the fiscal second quarter ended July 31: 

• Earnings per share: $1.56 adjusted, vs. $1.25 expected by Refinitiv’s consensus estimates
• Revenue: $137.74 billion vs. $135.48 billion expected by Refinitiv estimates
• U.S. same-store sales: up 9.3% vs. gain of 5.4%, expected by StreetAccount survey

In the second quarter, Walmart reported net income rose to $6.48 billion, or $2.27 per share, from $3.61 billion, or $1.26 per share, a year earlier.

Excluding items, the company earned $1.56 per share, higher than the $1.25 expected by analysts surveyed by Refinitiv. Among the excluded items are 10 cents a share in restructuring costs. In July, the company cut corporate positions across its business, but did not specify the number of jobs that were eliminated.

Total revenues rose 5.6% to  $137.74 billion from $130.38 billion a year earlier, outpacing Wall Street’s expectations of $135.48 billion.

Walmart customers shopped less frequently, but bought more when they did. The average ticket rose by 27% during the second quarter, as transactions fell by 14%.

The retailer said it spent about $1.5 billion on costs related to Covid-19. During the pandemic, Walmart has hired more than 400,000 hourly workers to fulfill online orders, clean stores and stock shelves.

Walmart’s international net sales fell by 6.8% to $27.2 billion, as government-mandated closures during the pandemic limited shopping in India, Africa and Central America.

Sam’s Club membership increased by more than 60% in the quarter — the highest quarterly increase in more than five years. The warehouse club’s e-commerce sales grew 39% and its same-store sales rose 13.3%.

Walmart Chief Financial Officer Brett Biggs told CNBC that the retailer could get another bounce, if there’s further stimulus.

“Stimulus was definitely impactful to the consumer in the second quarter, and we’re watching what’s going on in Washington, and how we’re going to progress with a new stimulus package,” he said. “I think certainly it would be helpful for consumers.”

However, he said, families may pull back or spend differently during back-to-school season as students prepare to learn remotely or go to school just a few days each week.

Compared with previous years, he said, the pandemic “has made back-to-school a little more uncertain” and “a little more choppy.”

Walmart did not provide a financial outlook for the rest of the year. It withdrew guidance in the first quarter, saying that many factors could change its performance including additional government stimulus, the level of consumer confidence and the length of the pandemic.

Shares of Walmart, which have a market value of $384 billion, have gained more than 14% since the start of the year. While other retailers have been hurt by closed stores and a weakening economy during the pandemic, Walmart has benefited from selling essential items like food and having strong online operations. 

—CNBC’s Bertha Coombs contributed to this story.

Read the complete press release here.