The data: Nearly 2 in 5 (37.9%) online grocery shoppers said they used a rapid delivery service for “most” or “all, or almost all” of their purchases over the past year, per Coresight Research data cited in Grocery Dive. That suggests rapid delivery has become a routine way for many US shoppers to stock their kitchens.

Zooming out: Walmart moved early to make fast delivery a core part of its grocery business, and that head start still shows up in the numbers.

Walmart’s Express Delivery, which guarantees orders in under 3 hours for a $9.99 fee, saw usage rise more than 60% YoY last year, the retailer said. Those gains are helping drive Walmart’s overall grocery ecommerce sales, which we expect to rise 16.3% YoY this year to $73.52 billion—well ahead of Amazon, which we expect to grow 8.8% to $52.49 billion.

Amazon is racing to close that gap by expanding same-day perishables delivery to more than 2,300 cities and towns. The move is already gaining traction: In markets where the service is available, nine of the top 10 best-selling items are now perishables, a sign shoppers are turning to the faster service for everyday needs.

Kroger, which we expect to increase its online grocery sales by 13.6% YoY this year, is chasing the same shift. Meanwhile, the broader market continues to expand, with US online grocery sales rising 11.1% last year and projected to grow another 10.0% this year.

Implications for retailers: Walmart helped make rapid delivery table stakes. Its early investment in low-cost, guaranteed delivery windows trained shoppers to expect speed, and the 60% jump in Express Delivery usage suggests that behavior is becoming habitual. Shoppers who trust a retailer with dinner ingredients tend to come back for other purchases, helping explain why Walmart’s lead over Amazon continues to widen.

Amazon’s push to fold fresh groceries into same-day delivery shows it understands the importance of speed, and the strategy is already boosting order frequency where it’s available. But closing a gap built on Walmart’s store density and delivery infrastructure will take time.

That leaves the rest of the market in a tougher spot. As rapid delivery becomes the baseline, retailers that can’t reliably meet those expectations risk falling further behind.

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