One of the hottest discount supermarket chains in the U.S. is partnering with Instacart to offer grocery delivery—a service once reserved primarily for high-end food retailers and high-income customers.

The move by German grocery chain Aldi, which will test the service in Dallas, Atlanta, and parts of Los Angeles starting August 31, is a sign of how competitive the supermarket landscape has become as food retailers look for every edge possible in a fast-changing marketplace.

“Aldi follows the digital world and e-commerce just like everyone else in the business,” Scott Patton, Aldi’s vice president of corporate buying, tells Fortune. “Online grocery retailing will be part of the future.”

The e-commerce shake-up in the rest the retail has been slow to hit food sales, with only 9% of U.S. adults reporting that their households order groceries online at least once a month, according to a recent poll from Gallup. However, the low use rate suggests a “theoretically enormous potential for growth,” according to Gallup.

Discounters like Aldi, known for its no-frills stores and highly coveted private label, have put pressure on traditional grocers, which are also trying…