An online e-commerce search engine is easy to put in place. Scaling it to serve millions of users, adding a marketplace to provide thousands of products, supporting multiple offers, prices and stocks on the same product are additional challenges more difficult to address. And what if, in addition, you mix your online search engine with the activity of thousands of physical stores? In this talk we explain how we addressed all these challenges in the context of the largest retail group and online grocery store in France. The constraint of multiple physical stores backed by the online search engine introduces additional challenges that we emphasize and address in detail. Our point of view, as we explain the challenges and solutions, is both technical and functional.