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# Apollo Federation
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Support for Apollo Federation allowing microservice architecture with federated GraphQL schemas.
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## Capabilities
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### Federated Types
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```python { .api }
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class FederatedObjectType(ObjectType):
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    """Object type with Apollo Federation support."""
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    def __init__(self, name: str): ...
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    def reference_resolver(self, resolver_func: Callable):
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        """Set entity reference resolver."""
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class FederatedInterfaceType(InterfaceType):
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    """Interface type with Apollo Federation support."""
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    def __init__(self, name: str): ...
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    def reference_resolver(self, resolver_func: Callable):
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        """Set entity reference resolver."""
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```
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### Federated Schema
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```python { .api }
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def make_federated_schema(
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    type_defs: Union[str, list[str]],
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    *bindables,
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    **kwargs
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) -> GraphQLSchema:
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    """Create Apollo Federation-compatible schema."""
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```
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## Usage Examples
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```python
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from ariadne.contrib.federation import FederatedObjectType, make_federated_schema
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type_defs = """
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    extend type User @key(fields: "id") {
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        id: ID! @external
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        posts: [Post!]!
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    }
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"""
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user_type = FederatedObjectType("User")
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@user_type.reference_resolver
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def resolve_user_reference(representation):
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    return get_user_by_id(representation["id"])
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schema = make_federated_schema(type_defs, user_type)
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```