About JustAPI

JustAPI is a Python web framework for building APIs, powered by a Rust core. It provides the same developer experience as FastAPI — decorator syntax, Pydantic models, dependency injection — while moving the entire networking stack out of Python.

Python writes the logic. Rust does everything else.

Python is excellent for application logic. It’s readable, has a rich ecosystem, and developers love it. But it has limitations for networking:

• The GIL prevents true parallelism in Python handlers.
• Python HTTP servers (uvicorn, gunicorn) add overhead.
• TLS termination, connection management, and routing are all CPU-bound.

JustAPI solves this by implementing these critical paths in Rust using:

• hyper — HTTP/1.1 and HTTP/2 implementation
• tokio — asynchronous runtime
• rustls — TLS termination without OpenSSL
• matchit — radix-trie routing
• PyO3 — seamless Python ↔ Rust boundary

1. FastAPI-compatible. Existing FastAPI apps migrate with minimal changes.
2. Rust-first. If it can be in Rust, it must be in Rust. Python is for application logic only.
3. Production-ready from day one. Built-in auth, rate limiting, circuit breakers, and observability.
4. Honest performance claims. Every benchmark number in the docs is reproducible on the documented hardware.

Kernel → epoll/io_uring
  → Connection Manager (tokio)
  → TLS (rustls)
  → HTTP parse (hyper)
  → Router (matchit)
  → Middleware chain (Rust: auth, CORS, rate-limit)
  → Python boundary (PyO3)
  → Application code (async Python)
  → Rust serializer (serde_json / simd-json)
  → Response write → Socket

• Alternatives, Inspiration & Comparisons
• History, Design & Future
• Benchmarks & Performance
• Repository Management