The test site is located at a Walmart store in Salem, New Hampshire, about 40 minutes northwest of Boston.
When I arrived, Walmart representatives led me to the back of the store, through a pair of double doors and down this narrow, fluorescent-lit hallway.
The hallway led us into the rectangular, 20,000-square-foot warehouse that's home to Alphabot.
The warehouse is small compared to Amazon fulfillment centers, which can range between 400,000 square feet and one million square feet.
The Alphabot system is essentially a grid of shelving that stores grocery items. It can hold about 20,000 different products.
Human employees at the Salem store pick fresh items, such as apples and lettuce, for online grocery orders. Alphabot handles everything else, such as canned soup, frozen foods, refrigerated milk, and light bulbs.
The items are stored inside these blue bins, of which there are more than 16,000.
Walmart's online grocery store includes many non-food items that can be found in various departments of its vast supercenters. Alphabot stores shoppers' most frequent purchases, based on Walmart's sales data.
Inside Alphabot, these wheeled robots whir quietly as they move vertically and horizontally along the shelving system, retrieving and depositing bins. The bots are about 2 feet wide by 2.5 feet long.
Thirty of these robots operate in the Salem Alphabot. The system will eventually ramp up to add 20 more bots.
Unlike many other automated fulfillment solutions on the market, Alphabot robots don't need lifts or pulleys. They move vertically and horizontally on their own.
This lift-free mobility is an important feature of Alphabot because it saves space, according to John Lert, the CEO of Alert Innovation, which built the system for Walmart. The smaller the Alphabot, the easier and cheaper it is to build onto Walmart stores in the future.
Bins appear on one side of the station filled with loose products. Workers remove the products from those bins and place them inside shopping bags in an adjacent bin.
The system lights up the shopping bag where workers should place an item, to help guide them to the correct placement.
When Walmart customers arrive at the store to pick up their orders, employees use these touch-screen computers to retrieve their groceries.
After retrieving an order, employees stack them on these rolling carts for easy transport to customers' cars. Walmart also offers delivery to customers' homes.
After we watched Alphabot fill orders, a Walmart employee demonstrated how workers stock the system with products.
First, employees scan the products and enter an expiration date. They they place the items in a bin, which a bot carries away to storage.
Walmart isn't yet planning a nationwide rollout of Alphabot, but analysts are already betting that it could be part of a winning strategy against competitors like Amazon and Kroger.
Jefferies analysts crowned Walmart's online fulfillment strategy, including Alphabot, as "best in breed" in a recent 44-page research report comparing the fulfillment methods of major online grocers.
The analysts praised the company for pursuing small grocery warehouses, which the industry calls micro fulfillment centers, instead of giant standalone fulfillment centers, like the kind that Kroger is building with Ocado.
The smaller warehouses are less expensive to build and take advantage of Walmart's existing real estate to keep fulfillment as close to customers as possible, analysts said. This helps maximize convenience for shoppers and minimize last-mile delivery costs for Walmart.
"Walmart's heightened focus on testing innovative technology, expansive store footprint, and leading market share have enabled it to become the clear front runner among the traditional retailers when it comes to omnichannel grocery offerings," the analysts wrote.