As retail giants Amazon and Walmart compete to be consumers’ first choice for their daily needs, the two companies view delivery time as a key factor in customer loyalty.

Amazon, for its part, said in its second-quarter earnings call last week that faster delivery speeds are leading to higher consumer spending in key consumer goods categories.

“We’ve achieved our fastest speeds ever this year, which continues to strengthen us in areas like our everyday essentials,” Brian Olsavsky, the e-commerce company’s SVP and CFO, told analysts. “This includes items like non-perishable food and health, beauty and personal care items, and Prime members are shopping more frequently while also spending more on Amazon. Overall sales increased 11% year over year.”

CEO Andy Jassy noted that faster delivery—over 5 billion shipments are delivered same-day or next-day—significantly increases customer engagement, especially in these essential categories. This efficiency not only enables higher shopping frequency, but also increases customer loyalty and reinforces Amazon’s position as the preferred retailer.

Walmart also clearly values ​​speedy order fulfillment. The company focused on this area in its first annual Adaptive Retail Report late last month, highlighting that 58 percent of consumers surveyed did not want to wait more than a day for grocery delivery and that 22 percent expected their groceries in one to two hours.

The inclusion of this result speaks to Walmart’s efforts to shorten its delivery times and increase consumer adoption of its on-demand delivery channels. In fact, the company is increasing its speed of order fulfillment worldwide.

“As in the U.S., the international team is improving delivery speed across all markets. In India, same-day delivery orders grew over 150% in the quarter and are now available in 20 major cities,” CEO Doug McMillon told analysts at the company’s latest earnings call. “One-hour delivery in China increased to 55 million orders as customers sought convenience during the Chinese New Year. And in Chile, 60% of e-commerce orders are delivered the same day.”

Currently, Amazon leads consumer retail spending by a wide margin, according to PYMNTS Intelligence’s Whole Paycheck Report. The study, which examines earnings reports from all companies as well as data from the U.S. Census Bureau and Bureau of Economic Analysis, estimates that Amazon had a 10% share of total consumer retail spending at the end of last year, while Walmart captured 7.3% of it.

Overall, consumers expect fast delivery. Results from the January issue of the PYMNTS Intelligence Real-Time Payments Tracker® show that 78% of consumers look for same-day or next-day delivery when making a purchase.

As the two major retailers compete for fast delivery, Amazon’s aggressive push to increase delivery speed has already shown tangible benefits, translating into higher consumer spending and stronger customer loyalty. Meanwhile, Walmart is not far behind, accelerating its efforts to meet rising consumer demand for fast and efficient service at home and abroad. As both giants vie for the top spot, their success will increasingly depend on their ability to not only deliver products, but also deliver them exceptionally quickly and conveniently. In an environment where the vast majority of consumers prefer fast delivery, the future is likely to bring even more innovation and competition in the quest to redefine instant gratification.