A unified API experience is crucial for creating an omnichannel shopping experience, and Apollo GraphOS is the perfect platform to achieve this by connecting all data sources in a supergraph. A federated GraphQL architecture splits services into subgraphs, allowing each team to own a smaller domain while providing a single, unified schema for clients to consume. By defining a user ID as the key field using the `@key` directive, client developers can access and manipulate user data across multiple channels, creating intricate queries that span across many subgraphs. Loyalty programs can also be integrated into the supergraph, allowing for rewards or discounts to be offered based on user actions across different channels. Ultimately, a retail supergraph provides the flexibility and scalability needed to power modern retail applications and deliver a seamless omnichannel shopping experience.