With Docker. A Dockerfile describes exactly how to build and run your app. Anyone (or any server) with Docker can run it identically:

FROM python:3.12-slim

WORKDIR /app
COPY requirements.txt .
RUN pip install --no-cache-dir -r requirements.txt

COPY . .
CMD ["uvicorn", "main:app", "--host", "0.0.0.0", "--port", "8000"]

Line by line: start from a Python image, install dependencies, copy your code, run uvicorn. The --host 0.0.0.0 is critical — it means "listen on all network interfaces" so the container is reachable from outside.

A health check endpoint tells the deployment platform your app is alive and ready. Platforms like Railway and AWS check it periodically and restart your app if it stops responding:

from datetime import datetime

startup_time = datetime.utcnow()

@app.get("/health")
def health():
    return {
        "status": "healthy",
        "uptime_seconds": (datetime.utcnow() - startup_time).total_seconds(),
        "version": "1.0.0"
    }

Keep it simple — no database calls, no external dependencies. The health check should test that your app process is running, not that every downstream service is up.

When the platform sends a shutdown signal (SIGTERM), your app should finish processing current requests before exiting — not cut them off mid-response:

import signal
import asyncio

def handle_shutdown(signum, frame):
    print("Shutting down gracefully...")
    # FastAPI/uvicorn handle this automatically with --timeout-graceful-shutdown

signal.signal(signal.SIGTERM, handle_shutdown)

Uvicorn handles most of this for you. The key setting is --timeout-graceful-shutdown 30 — it gives in-flight requests 30 seconds to complete before forcing a shutdown.

Pin exact versions:

Never use fastapi>=0.110.0 in production — an unpinned dependency could update and break your app. Use pip freeze > requirements.txt to capture exact versions from your working environment.

The deployment flow: push code, Docker builds the image, the platform runs the container, health checks confirm it's alive. If the health check fails, the platform rolls back to the previous version automatically.