Security considerations in GraphQL Federation

GraphQL Federation unlocks powerful capabilities for building modular, scalable APIs, but it also introduces new security challenges.

In a federated architecture, multiple services collaborate to serve a single GraphQL API, which means security must be handled carefully across all layers: the subgraphs, the gateway (or supergraph), and the network itself.

In this guide, we'll explore the key security considerations when implementing GraphQL Federation, and how platforms like Grafbase simplify securing your federated graph.

In a monolithic GraphQL server, you typically deal with:

• One schema
• One set of authentication and authorization rules
• One runtime environment

However, in a federated system:

• You have multiple independently deployed services (subgraphs).
• Each subgraph can be owned by a different team or domain.
• Security must be coordinated across services, not just enforced centrally.

Without careful design, federation can open vulnerabilities like:

• Inconsistent authentication across services
• Overexposed internal data
• Authorization bypasses across subgraphs
• Denial of service (DoS) via inefficient cross-service queries

Authentication verifies the identity of the caller.

In a federated system, you must decide:

• Does the supergraph (gateway) authenticate the client and forward trusted - identity to subgraphs?
• Or does each subgraph re-authenticate independently?

Best practice: Authenticate once at the supergraph. Then forward identity metadata (e.g., user ID, claims, roles) to subgraphs via trusted headers.

Grafbase, for example, authenticates requests at the edge and ensures consistent identity across the entire federated graph automatically.

Authorization checks whether a user is allowed to perform an action.

Even if authentication is centralized, authorization must be enforced locally within each subgraph:

• A subgraph should never trust that upstream queries are safe.
• Every resolver must verify permissions based on the forwarded identity.

Best practice: When you adopt federation with existing subgraphs, authorization logic should be owned and enforced inside each subgraph to avoid privilege escalation.

For example, if a shopping-cart subgraph exists in an e-commerce application, it would be the subgraph's responsibility to return only the authenticated user's shopping cart.

When a supergraph composes queries by calling subgraphs, those internal service calls must be secured.

Risks:

• If subgraphs accept unauthenticated traffic, attackers could bypass security by directly accessing subgraph endpoints.

Best practice: Subgraphs should only accept traffic from trusted sources (the supergraph or internal network) often enforced via network policies, mTLS, or API gateways.

Grafbase handles these internal communications securely under the hood without requiring manual network configurations.

Federation can unintentionally surface internal data if schema boundaries aren't tightly controlled. This is especially risky when combining subgraphs owned by different teams or domains.

Risks include:

• Exposing internal-only types or fields
• Leaking debugging or infrastructure metadata
• Revealing sensitive service relationships through type extensions

Best practice: Control your schema surface area with strict visibility rules.

Grafbase gives you schema-level control to define exactly what gets exposed in the supergraph. You can keep internal types private by design and ensure only intended APIs are visible externally.

Federated queries can span multiple subgraphs. Malicious users could craft extremely expensive queries that:

• Traverse deeply nested data
• Perform large cross-service joins
• Cause performance degradation (resource exhaustion)

Best practice:

• Enforce query complexity limits and depth limits at the gateway level.
• Monitor and throttle suspicious traffic patterns.
• Paginate responses where possible.

Grafbase automatically applies query complexity analysis and offers built-in protections against abusive federated queries.

Grafbase is designed to make securing federated GraphQL deployments easier:

• Built-in authentication and JWT validation.
• Secure supergraph-subgraph communication out of the box.
• Schema validation tools for clean federation.
• Rate limiting.
• Automatic query complexity analysis.

By using Grafbase Federation, you get the benefits of a unified, modular API architecture without taking on unnecessary security risks.

GraphQL Federation introduces exciting flexibility — but it must be matched with a strong security posture.

By centralizing authentication, decentralizing authorization, securing service-to-service communication, and carefully designing schemas, you can build secure, scalable federated APIs.

Platforms like Grafbase dramatically reduce the operational burden, helping you ship federated systems with confidence and security by default.

Ready to build a secure supergraph?

Check out our introduction to GraphQL Federation or get in touch with our team!