Week 6 — Real backend (FastAPI + SQLite)

One Python file. A real API. Free docs.

The walkthrough

1. One Python file. A real API. Free docs.
2. Education Series · Module 6 · Real Backend with FastAPI + SQLite
3. Fast · Type hints = validation · Auto docs · Async · Python you already know
4. One file · No server · ACID · Runs everywhere · Free · 281TB max
5. api/ · ├── main.py · ├── models.py · ├── db.py · ├── routes/ · └── data/contacts.db
6. python -m venv .venv then activate
7. pip install fastapi uvicorn[standard] sqlmodel
8. from fastapi import FastAPI · app = FastAPI() · @app.get('/') · def root(): return {'ok': True}
9. uvicorn main:app --reload
10. Browser at http://localhost:8000/docs showing Swagger UI
11. class Contact(SQLModel, table=True): id: int = Field(primary_key=True); name: str; email: str; ...
12. SQLModel.metadata.create_all(engine) on startup
13. @app.post('/api/contact') · def create(contact: Contact): db.add(contact); db.commit(); ...
14. Add /api/contact POST and /api/contacts GET routes. SQLModel session, dependency-injected.
15. def get_session(): with Session(engine) as s: yield s
16. app.add_middleware(CORSMiddleware, ...)
17. Try it out
18. select * from contact
19. fetch('http://localhost:8000/api/contact', { method: 'POST', body: ... })
20. Form fills, submit, 200, row appears in SQLite
21. A send_email helper using Postmark, called after the insert
22. def list_contacts(api_key: str = Header()): checking against env var
23. X-API-Key: ...
24. Same pattern: model, route, validation, insert
25. ContactCreate (input) vs Contact (DB)
26. alembic init · alembic revision --autogenerate
27. import logging · structured logs to a file + console
28. BackgroundTasks for the email send so the response is fast
29. /docs now shows every route, every model, every error
30. flyctl launch then flyctl deploy
31. flyctl volumes create data -s 1
32. $0/mo on free tier · $1.94/mo for the volume · still cheaper than Heroku
33. When: 50+ concurrent writes/sec · multi-region · giant joins
34. 1. SQL injection · 2. No auth on admin routes · 3. Missing CORS · 4. Logging secrets
35. Static site → FastAPI → SQLite → Postmark
36. HOMEWORK: Move ONE Netlify Function to FastAPI. Run it locally. Hit it from your site.
37. NEXT WEEK: Stripe payments — first paid product

— Jake Morris · Oklahoma veteran · localmodeldojo.com