Frameworks

Authorization for FastAPI applications with Cerbos

Implement fine-grained roles and permissions for FastAPI with Cerbos

Extend FastAPI roles

Fine grained access controls extending the roles defined in FastAPI

Enrich with context

Request time attribute based authorization enables more contextual access controls

Avoid token bloat

Independent authorization logic avoids bloated tokens and workarounds

How Cerbos works with FastAPI

Building authorization logic inside FastAPI quickly becomes a maintenance burden. Hard-coded role checks scatter across controllers and middleware, and every permission change requires a code deploy.

Cerbos replaces scattered authorization logic with a single API call. You define fine-grained policies in YAML, and the Cerbos PDP evaluates them at request time using roles, attributes, and any context you provide.

With Cerbos your FastAPI application stays focused on business logic while authorization policies evolve independently, managed by product or security teams without touching code.

Policy-as-codeHuman-readable YAML policies managed like source code Scalable PDPStateless policy decision point with sub-millisecond latency Centralized managementManage, test, and deploy policies from a single control plane

How Cerbos works with FastAPI

Add the Cerbos SDK to your FastAPI project, Install the appropriate Cerbos SDK and configure it within your FastAPI application.
Replace inline auth checks with a Cerbos call, Swap scattered permission logic for a single API call that evaluates policies at request time.
Define policies in YAML, Write human-readable authorization rules covering roles, attributes, and conditions, versioned alongside your code.
Cerbos evaluates at request time, Every request is authorized against the latest policies with sub-millisecond latency, no redeploy needed.

FAQ

How do I integrate Cerbos with FastAPI?

Cerbos integrates with FastAPI through a lightweight SDK or REST/gRPC API call. You replace hard-coded permission checks in your controllers or middleware with a single call to the Cerbos PDP, which evaluates your policies at request time.

Will Cerbos slow down my FastAPI application?

No. The Cerbos PDP runs alongside your application (as a sidecar or service) and delivers sub-millisecond authorization decisions. Because it's stateless and scales horizontally, it adds negligible latency to request processing.