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# Apollo GraphQL
## Docs > Schema Design > Federated Schemas
- [Introduction to Apollo Federation](https://www.apollographql.com/docs/graphos/schema-design/federated-schemas/federation.md): Learn how Apollo Federation helps you declaratively orchestrate your APIs and services into a unified, federated GraphQL API using a microservices architecture.
- [Federated Schemas](https://www.apollographql.com/docs/graphos/schema-design/federated-schemas/schema-types.md): Learn about subgraph, supergraph, and API schemas in federated GraphQL architectures.
- [Schema Composition](https://www.apollographql.com/docs/graphos/schema-design/federated-schemas/composition.md): Learn about schema composition in a federated GraphQL architecture. Explore strategies for handling conflicting types and directives.
- [Value Types in Apollo Federation](https://www.apollographql.com/docs/graphos/schema-design/federated-schemas/sharing-types.md): Learn how to share GraphQL types and fields across subgraphs with Apollo Federation.
## Docs > Schema Design > Federated Schemas > Federation Reference
- [Apollo Federation Changelog](https://www.apollographql.com/docs/graphos/schema-design/federated-schemas/reference/versions.md): Understand changes between Apollo Federation major and minor versions.
- [Apollo Federation Directives](https://www.apollographql.com/docs/graphos/schema-design/federated-schemas/reference/directives.md): Reference for GraphQL federation directives including @key, @extends, @sharable, @override, @requires and more.
- [Composition Rules](https://www.apollographql.com/docs/graphos/schema-design/federated-schemas/reference/composition-rules.md): Learn what rules subgraph schemas must follow to successfully compose in a federated GraphQL architecture.
## Docs > Schema Design > Federated Schemas > Federation Reference > Subgraph Reference
- [Apollo Federation Subgraph Specification](https://www.apollographql.com/docs/graphos/schema-design/federated-schemas/reference/subgrap