Walmart is making a lot of progress in adapting its big-box approach to the 21st century and has become the second largest online retailer in the U.S. after Amazon. By giving workers raises and investing heavily in tech, its U.S. division has improved customer service and saw comparable sales rise each quarter in 2015. It is hoping to build on that with a major reset of its food business, which accounts for more than half of its sales, with a bigger focus on organic and fresh food, and by offering curbside order pick up. The retailer has also proven it can hold its own with the tech giants, rollouting out Walmart Pay across the U.S. But huge challenges remain for the world’s largest company. Its e-commerce growth lags that of its main rivals. Its Sam’s Club unit is struggling to keep up with Costco. What’s more, its international division is being buffeted by a strong U.S. dollar that is eating into profits. Total sales fell for the first time in 2015.

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