How to containerize a FastAPI app with Docker

Dockerizing a FastAPI App

A production-ready FastAPI Dockerfile should be minimal, use layer caching effectively, and run as a non-root user.

Dockerfile

FROM python:3.12-slim

WORKDIR /app

# Copy requirements first — cached if unchanged
COPY requirements.txt .
RUN pip install --no-cache-dir -r requirements.txt

# Copy application code
COPY . .

# Create non-root user
RUN adduser --disabled-password --gecos '' appuser
USER appuser

EXPOSE 8000

CMD ["uvicorn", "app.main:app", "--host", "0.0.0.0", "--port", "8000", "--workers", "4"]

.dockerignore

__pycache__
*.pyc
.env
.git
tests/
alembic/
*.md

Copying requirements.txt before the application code is the critical layer caching trick. Docker only re-runs pip install when requirements.txt changes — not on every code change.

Build and run

docker build -t my-api .
docker run -p 8000:8000 --env-file .env my-api

For multiple services, use Docker Compose to orchestrate the app, PostgreSQL, and Redis together. Never bake .env files into the image — mount them at runtime.