Amazon is planning a major roll-out of an online grocery business that it has been quietly developing for years, targeting one of the largest retail sectors yet to be upended by e-commerce, according to two people familiar with the situation. While food is a low-margin business, Amazon could outperform similar online grocery services by delivering orders for higher-margin items like electronics at the same time. One of the people familiar with AmazonFresh’s expansion plans said new warehouses will have refrigerated areas for food, but also space nearby to store up to one million general merchandise products, in some cases. The company has been testing AmazonFresh in its hometown of Seattle for at least five years, delivering fresh produce such as eggs, strawberries and meat with its own fleet of trucks.