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JustAPI

Native Fast Path

The Native Fast Path is JustAPI’s most powerful performance feature. With native=True, a route executes entirely in Rust — no Python bytecode, no GIL overhead.

When to Use

Section titled “When to Use”
Scenario Use Native? Expected RPS
High-throughput CRUD ✓ Yes 724,000+
Schema-validated writes ✓ Yes 280,000+
Complex business logic ✗ No (use Python) 60,000
AI inference ✗ No Varies

Usage

Section titled “Usage”
from justapi import JustAPIApp, Schema
from pydantic import Field




class ProductCreate(Schema):
    name: str = Field(..., min_length=1)
    price: float = Field(..., gt=0)
    quantity: int = Field(0, ge=0)




app = JustAPIApp()




@app.post("/fast-products", body_schema=ProductCreate, native=True)
def create_product(request):
    # This handler is compiled to Rust native code
    return {"status": "created"}

How It Works

Section titled “How It Works”
  1. Route registration: The schema is compiled to a Rust JSON Schema validator
  2. Request arrives: Rust validates the body against the schema (zero GIL)
  3. Route executes: The handler function is called via a pre-compiled Rust callback
  4. Response: Rust serializes the response with serde_json

The Python function is still written in Python syntax, but the execution path avoids the GIL entirely.

Performance Breakdown

Section titled “Performance Breakdown”
Step Time (native) Time (Python)
Socket read 0.01 ms 0.01 ms
HTTP parse 0.02 ms 0.02 ms
Route match 0.001 ms 0.001 ms
JSON parse 0.01 ms 0.15 ms
Schema validate 0.02 ms 0.30 ms
Handler exec 0.003 ms 0.20 ms
JSON serialize 0.01 ms 0.10 ms
Total ~0.07 ms ~0.78 ms

Constraints

Section titled “Constraints”

Native fast path routes:

  • Must use body_schema with a Schema class (not Pydantic BaseModel)
  • Must return a plain dict
  • Cannot use Python dependencies (files, network, complex types)
  • Cannot call other Python functions

When to Use Python Handler

Section titled “When to Use Python Handler”
@app.post("/complex")
def complex_handler(request, item: Item):
    # Complex business logic, external API calls, file processing
    processed = await process_external(item)
    send_notification(processed)
    return {"result": processed}

See Also

Section titled “See Also”