A collection of hands-on, high-quality mini projects designed to explain complex backend, system design, and software engineering concepts simply and effectively.
This repository is a learning resource where each project focuses on a single "hard" concept, breaking it down into a tiny, runnable implementation that anyone can understand.
| Project | Concept | Language | Description |
|---|---|---|---|
| Database Migration | Schema Migrations | Python | A from-scratch migration engine explaining up(), down(), and history tracking. |
| Multi-Factor Authentication | TOTP / 2FA | Python | A from-scratch TOTP implementation (RFC 6238) with FastAPI 2FA endpoints and QR onboarding — compatible with Google Authenticator. |
| Rate Limiter | Token Bucket Algorithm | Python | A complete token bucket rate limiter implemented as FastAPI middleware with per-route overrides, X-RateLimit-* headers, and stress testing. |
| App Scheduler | Background Job Scheduling | Python | A Flask-based scheduler with APScheduler, Gunicorn, and Kubernetes deployment examples. |
| Feature Flag | Feature Flags / Toggles | Python | A from-scratch feature flag engine with rule-based targeting, percentage rollouts, A/B variants, hot-reload, and an admin web dashboard. |
Modern frameworks (Django, FastAPI, Spring) hide a lot of magic. The goal of this repository is to remove the magic by building "the basics" from scratch.
Each project follows these rules:
- No Magic: Uses standard libraries or minimal dependencies.
- Pedagogical: Heavily commented code explaining why things are done.
- Runnable: Can be started in seconds with a single command.
- Standalone: Each folder is a complete, independent project.
- Isolated: Each project has its own
.venv— no shared dependencies.
- Python 3.13+
uv— fast Python package manager
Every project follows the same setup pattern:
# 1. Navigate into the project
cd <project-name>
# 2. Create an isolated virtual environment
uv venv
# 3. Install dependencies
uv sync
# 4. Run (see each project's README for specific commands)
uv run main.py # or uv run demo.py, etc.Each project has its own
.venvandpyproject.toml, keeping dependencies fully isolated between projects.
Created by AlwaysSany as a personal experiment lab for deep-diving into the "basics" of modern software systems.