Walmart is the biggest employer in the country and the largest retail company in the world, but it's currently locked in a battle for consumers' dollars with Amazon that dominates online shopping. Walmart hopes to leverage one staggering fact: 90% of Americans live within 10 miles of a Walmart store.

In a recent talk at the South by Southwest (SXSW) conference in Austin, Walmart's chief technology officer Jeremy King revealed how the company is thinking of new ways to take advantage of its vast physical footprint to make the shopping experience more convenient for customers, whether in-person or online.

The key: Walmart's stores are doubling as warehouses for online shoppers. It's something other retailers, including Target, are also trying to do to compete with Amazon. But no other traditional retailer has Walmart's scale. "The greatest part about Walmart using the Walmart store is that store is already profitable," King says. "If you can use those as warehouses, it's a game changer for us. Most of the cost of e-commerce is in shipping. If you think about the ability to have deployed inventory five miles away from 70% of Americans, and you can figure out that last mile, you're talking about a difference in profitability."