fastrapi

FastrAPI (Fast + Rust + API)

FastrAPI is a high-performance web framework that supercharges your Python APIs with the power of Rust. Built on Axum and PyO3, it delivers unmatched speed, type safety, and developer-friendly Python syntax. Create robust, async-ready APIs with minimal overhead and maximum throughput. FastrAPI is your drop-in replacement for FastAPI, offering familiar syntax with up to 33x faster performance.

Key Features

• Lightning Speed: Powered by Rust and Axum, FastrAPI delivers up to 33x faster performance than FastAPI, making your APIs scream.
• Python-First: Write clean, familiar Python code, no Rust knowledge needed. FastrAPI handles the heavy lifting behind the scenes.
• Ironclad Type Safety: Inherits Rust's robust type system for rock-solid reliability, catching errors before they hit production.
• Pydantic Powered: Seamless integration with Pydantic for effortless request and response validation, keeping your data in check.
• Async Native: Built on Tokio's async runtime, FastrAPI maximizes concurrency for handling thousands of requests with ease.
• Ultra Lightweight: Minimal runtime overhead with maximum throughput.
• Drop-in Replacement: Drop-in compatibility with FastAPI's beloved decorator syntax, so you can switch without rewriting your codebase.

Is it as fast as claimed?

Yes. Powered by Rust and Axum, FastrAPI outperforms FastAPI by up to 33x in real-world benchmarks, with no compromises on usability. Check it out here

Do I need to know Rust?

Nope. FastrAPI lets you write 100% Python code while leveraging Rust's performance under the hood.

Can it handle complex APIs?

Absolutely. With full Pydantic integration and async support, FastrAPI scales effortlessly for small projects and enterprise-grade APIs alike.

Will it keep up with FastAPI updates?

Yes. FastrAPI mirrors FastAPI's decorator-based syntax, ensuring compatibility and instant access to familiar workflows.

Installation

uv

uv install fastrapi

pip

pip install fastrapi

Switch from FastAPI

- from fastapi import FastAPI
+ from fastrapi import FastrAPI

Get Started

from fastrapi import FastrAPI
app = FastrAPI()

@app.get("/hello")
def hello():
    return {"Hello": "World"}

@app.post("/echo")
def echo(data):
    return {"received": data}

if __name__ == "__main__":
    app.serve("127.0.0.1", 8080)

Now, test it with:

curl http://127.0.0.1:8080/hello

For the POST endpoint:

curl --location 'http://127.0.0.1:8080/echo' \
--header 'Content-Type: application/json' \
--data '{"foo": 123, "bar": [1, 2, 3]}'

Show Pydantic example

from pydantic import BaseModel
from fastrapi import FastrAPI

api = FastrAPI()

class User(BaseModel):
    name: str
    age: int

@api.post("/create_user")
def create_user(data: User):
    return {"msg": f"Hello {data.name}, age {data.age}"}

api.serve("127.0.0.1", 8080)

Show ResponseTypes Example

from fastrapi import FastrAPI
from fastrapi.responses import HTMLResponse, JSONResponse

api = FastrAPI()

@api.get("/html")
def get_html() -> HTMLResponse:
    return HTMLResponse("<h1>Hello</h1>")

api.serve("127.0.0.1", 8080)

Show Middleware Example

from fastrapi import FastrAPI
from fastrapi.responses import JSONResponse

from fastrapi.middleware import (
    CORSMiddleware,
    TrustedHostMiddleware,
    GZipMiddleware,
    SessionMiddleware
)

app = FastrAPI()

# TrustedHost Middleware
app.add_middleware(
    TrustedHostMiddleware, 
    allowed_hosts=["127.0.0.1", "localhost", "127.0.0.1:8000"],
    www_redirect=True
)

# CORS Middleware
app.add_middleware(
    CORSMiddleware,
    allow_origins=["*"],
    allow_methods=["GET", "POST"],
    allow_headers=["*"],
    allow_credentials=False
)

# 3. GZip Middleware
app.add_middleware(
    GZipMiddleware, 
    minimum_size=500,
    compresslevel=9
)

# 4. Session Middleware
app.add_middleware(
    SessionMiddleware,
    secret_key="super-duper-secret-key-change-this-in-prod-pwease-uwu-BUT-MAKE-IT-LONGER-NOW",
    session_cookie="fastrapi_session",
    max_age=3600,
    https_only=False
)

# ROUTES
# WARNING: ALWAYS return JSONResponse if it's JSON, to ensure proper serialization
@app.get("/")
def index() -> JSONResponse:
    return JSONResponse({"status": "running"})

@app.get("/heavy")
def heavy_data() -> JSONResponse:
    # response large enough to trigger GZip compression
    large_data = "x" * 1000
    return JSONResponse({
        "data": large_data,
        "note": "Check content-encoding header!"
    })

# Session Test: Increment a counter stored in the cookie
@app.get("/counter")
def session_counter(request) -> JSONResponse:
    # For now, this verifies the Middleware sets the cookie correctly.
    return JSONResponse({"message": "Session cookie should be set"})

if __name__ == "__main__":
    app.serve("127.0.0.1", 8000)

# Test with:
# curl -v -H "Host: 127.0.0.1" http://127.0.0.1:8000/
# curl -v -H "Origin: http://example.com" http://127.0.0.1:8000/

Performance

Benchmarks using k6 show it outperforms FastAPI + Guvicorn across multiple worker configurations.

🖥️ Test Environment

• Kernel: 6.16.8-arch3-1
• CPU: AMD Ryzen 7 7735HS (16 cores, 4.83 GHz)
• Memory: 15 GB
• Load Test: 20 Virtual Users (VUs), 30s

⚡ Benchmark Results

Framework	Avg Latency (ms)	Median Latency (ms)	Requests/sec	P95 Latency (ms)	P99 Latency (ms)
FASTRAPI	0.59	0.00	31360	2.39	11.12
FastAPI + Guvicorn (workers: 1)	21.08	19.67	937	38.47	93.42
FastAPI + Guvicorn (workers: 16)	4.84	4.17	3882	10.22	81.20

TLDR; FASTRAPI handles thousands of requests per second with ultra-low latency , making it ~33× faster than FastAPI + Guvicorn with 1 worker.

Comparison: FastAPI vs FastRAPI

Area	FastAPI	FastRAPI	FastRAPI wins?
Dependency resolution	Runtime inspect + reflection every request	One-time parsing at decorator → pre-built injection plan	✅
Fast-path for trivial endpoints	No special case: full kwargs/dependency work always	is_fast_path flag → skip deps, validation, kwargs	✅
Route lookup speed	Starlette regex router (slows with many routes)	papaya concurrent hashmap → O(1) lookup	✅
Middleware usability (Python)	@app.middleware often buggy / limited	Clean, working decorator + real execution	✅
Background tasks reliability	Fire-and-forget, errors usually swallowed	Proper JoinHandle + error logging	✅
WebSocket implementation	Starlette (solid but heavy)	Custom with bounded channels + clean async pump	✅
Startup-time error detection	Almost everything deferred to runtime	Full signature + dependency analysis at decorator time	✅
Concurrency & resource safety	asyncio + threadpool	Native Tokio + Rust memory & thread safety	✅
Deployment footprint	Heavy (uvicorn + many deps)	Tiny Rust binary + optional Python runtime	✅
Scaling to 10,000+ routes	Noticeable slowdown	Stays fast thanks to hashmap lookup	✅
JSON serialization flexibility	Hard to swap (monkey-patch needed)	Trivial to plug orjson / sonic-rs / simdjson	✅
response_model=None + raw Response return	Fully supported	serialization	❌ (for now)
APIRouter + include_router()	Yes, mature ecosystem	Not yet implemented	❌ (for now)
app.mount() / StaticFiles	Yes	Not yet implemented	❌ (for now)

Current Limitations

Some advanced features are still in development like:

• Logging/metrics
• A nice logging tool
• Async Middleware support
• Lifespan Events (@app.on_startup / @app.on_shutdown)
• Better error handling (currently shows Rust errors)
• Rate limiter (even FastAPI doesn't have it)
• Websockets
• Form/Multipart support
• Sub-APIs / Includes
• Security Utilities (OAuth2, JWT, etc.)
• Hot Reloading
• Rust integration
• Dependency injection
• Static file serving (UploadFile + axum::extract::Multipart)
• Testing support
• GraphQL support
• APIRouter + include_router(prefix=..., tags=..., dependencies=...)
• Respect response_model=None (allow raw Response / RedirectResponse returns)
• app.mount() for static files & sub-apps
• @app.exception_handler() + app.add_exception_handler()
• Proper Python-friendly error pages (no Rust tracebacks in production)
• lifespan= context manager (modern style)
• app.openapi() method (customizable spec)
• app.state (mutable app-wide state)
• app.openapi_tags= ordering in Swagger UI
• callbacks= and webhooks= in OpenAPI
• app.servers=, root_path, openapi_external_docs
• app.swagger_ui_parameters= customization
• separate_input_output_schemas in OpenAPI generation
• Hot reloading / watchfiles integration
• Built-in TestClient (starlette.testclient style)
• Metrics / Prometheus endpoint
• Advanced dependency scopes (request vs function)
• Full middleware ordering control
• Rust → Python FFI helpers for fast endpoints

Contributing

Contributions are welcome! Please feel free to submit a Pull Request.

• Fork the repository
• Create your feature branch (git checkout -b feature/amazing-feature)
• Commit your changes (git commit -m 'Add some amazing feature')
• Push to the branch (git push origin feature/amazing-feature)
• Open a Pull Request

Check out CONTRIBUTING.md for more details.

License

This project is licensed under the MIT License - see the LICENSE file for details.

Acknowledgments

Inspired by FastAPI Built with PyO3 and Axum

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