The FastAPI approach.
FastAPI builds Python APIs with validation, dependency injection, OpenAPI documentation, and support for asynchronous endpoints.
Turn your Python API into an app people can use.
Give your API a working application interface with Reflex. Build forms, tables, navigation, and server-side interactions in Python, then connect the services your team already maintains.
Build the application your team needs.
Put a custom interface around your services.
Bring it together with Reflex.
Defines the application interface, state, and event handlers in Python. Build user-facing forms, tables, charts, and navigation with UI components.
Keep the work you can build on.
Keep FastAPI as a service boundary. Reflex can call those endpoints while managing application state and the user interface, letting you deliver a complete workflow around an existing API.
Compare the details.
Compare what you can build, how you can extend it, and where it can run. Explore the sources for each product.
What this comparison covers
Compares FastAPI with the Reflex framework and its optional AI development and hosting products. Sources describe each product’s development model; these are not performance benchmarks.
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| Decision | FastAPI | Reflex |
|---|---|---|
| Primary abstraction | Defines typed API endpoints and generates API documentation. | Defines the application interface, state, and event handlers in Python. |
| User interface | Provides interactive API documentation; product UI choices belong to the application architecture. | Build user-facing forms, tables, charts, and navigation with UI components. |
| Validation and actions | Validates request data and supports reusable dependencies. | Handle UI actions in Python and call existing APIs, retaining server-side validation and authorization. |
Python teams building the whole application.
SellerX compared development with Reflex against its React and FastAPI stack. The World Bank uses Reflex alongside existing FastAPI services.
“With Reflex it is ten times faster than developing with React and FastApi.”
Know which part of Reflex you need.
Framework, AI development, hosting, and enterprise services have different responsibilities and entitlements.
Open-source framework
The Apache 2.0 Python framework is available independently of Build and managed hosting. Your app still depends on Reflex and its other packages.
Reflex Build
The AI development product generates and edits framework-based apps. Usage, private projects, repository access, and export entitlements belong to your plan.
Hosting and App Management
Managed deployment is an operating service. You can also self-host a framework app, providing its frontend, Python backend, configuration, and maintenance.
Enterprise
Enterprise packages and services have separate entitlements. Workspace SSO is distinct from app-user authentication. Authorization, auditing, and private deployment need configuration and an agreed operating plan.
Start with one workflow.
A focused pilot lets you validate the interface, business rules, and operating model before a wider rollout. The example below uses synthetic data.
Build a service request portal.
Document the endpoint
Use two staging requests and record the create, list, and status response contracts.
Create the interface
Build a form and request list in Reflex. Call the existing FastAPI endpoints from backend handlers.
Handle the lifecycle
Show request REQ-101 as queued, then completed. Make validation errors and network failures visible to users.
Verify the boundary
Confirm the persisted request matches the form, authentication reaches the service correctly, and retries do not duplicate work.
What a passing pilot looks like
A valid request is created once, appears in the list, and shows its saved status. Invalid inputs and unavailable services produce actionable errors.
Make the move one workflow at a time.
A clear first project. A foundation you can extend.
An API does not define the complete user journey. Design application state, navigation, permissions, and recovery paths alongside the existing service contracts.
Plan application authentication, authorization, monitoring, and maintenance with your team. The framework, Reflex Build, managed hosting, and enterprise services have separate responsibilities and entitlements.
Questions before you choose.
The practical details, before you make a move.
Why build with Reflex instead of FastAPI?
Give your API a working application interface with Reflex. Build forms, tables, navigation, and server-side interactions in Python, then connect the services your team already maintains.
Can Reflex call our existing FastAPI endpoints?
Yes. Call them from server-side Python handlers with your chosen HTTP client. Preserve the API’s authentication and validation rules and handle failures in the interface.
Can we choose where the Reflex app runs?
Yes. Use managed Reflex hosting or self-host the framework’s frontend and Python backend. Self-hosting includes responsibility for configuration, secrets, scaling, and operations.
How should we validate the first release?
A valid request is created once, appears in the list, and shows its saved status. Invalid inputs and unavailable services produce actionable errors.
Bring one workflow. Build a useful first version.
Install Reflex and start building your application in Python.