Migrating from FastAPI¶

FasterAPI is not a line-for-line fork of FastAPI, but many concepts map directly. Plan on touching imports, model types, and any code that assumed Pydantic or Starlette internals.

1. Install and import¶

FastAPI	FasterAPI
`pip install fastapi`	`pip install faster-api-web`
`from fastapi import FastAPI`	`from FasterAPI import Faster`
`app = FastAPI()`	`app = Faster()`

The PyPI distribution name is faster-api-web. The Python package directory is FasterAPI (capital F and API).

2. Replace Pydantic models with msgspec¶

Validation and JSON encoding use msgspec structs:

# FastAPI
from pydantic import BaseModel

class User(BaseModel):
    name: str
    email: str

# FasterAPI
import msgspec

class User(msgspec.Struct):
    name: str
    email: str

Field defaults, optional fields, and nested structs work with msgspec’s usual rules. If you relied on Pydantic-specific validators (@field_validator) or complex JSON Schema, reimplement that logic with plain Python or narrow msgspec types.

3. Routing and decorators¶

@app.get, @app.post, APIRouter-style grouping, path parameters, and Depends() are intended to feel familiar. Differences tend to be edge cases (custom Starlette routes, advanced middleware ordering). Port routes one module at a time and run tests.

4. Exceptions and responses¶

HTTPException, JSON responses, redirects, and file responses have near-equivalent types under FasterAPI. Check response headers and status codes in integration tests after migration.

5. OpenAPI and docs¶

OpenAPI generation is supported; field metadata may differ slightly from Pydantic’s schema extras. Regenerate your client or inspect /openapi.json after switching models.

6. Testing¶

Use TestClient from FasterAPI (httpx-based), similar to Starlette’s test client. Install httpx in the environment where you run tests (pip install httpx — it is included in the project’s dev extras but not in the minimal runtime install). Update imports and rerun your suite; fix any tests that imported Starlette types directly.

Suggested order of work¶

Add FasterAPI beside FastAPI in a branch; swap the app factory and deps.
Convert models to msgspec.Struct and fix type errors.
Run tests and fix request/response assumptions.
Measure latency/throughput in staging if performance is a goal.

If something you need is missing, open an issue with a minimal reproduction against the GitHub repo.