8.2Federation Architecture

+------------------+  +------------------+  +------------------+
| ProductService   |  | OrderService     |  | UserService      |
| Subgraph         |  | Subgraph         |  | Subgraph         |
|                  |  |                  |  |                  |
| type Product     |  | type Order       |  | type User        |
|   @key(id)       |  |   items: [Item]  |  |   @key(id)       |
|   name: String   |  |   customer: User |  |   name: String   |
|   price: Float   |  |                  |  |   email: String  |
+--------+---------+  +--------+---------+  +--------+---------+
         |                     |                     |
         +---------------------+---------------------+
                               |
                    +----------+----------+
                    |   Apollo Gateway    |
                    |   (Composed Schema) |
                    +---------------------+