Building CheckAPI: From Idea to Production in 6 Weeks with FastAPI and Next.js

I just launched CheckAPI - an open source API monitoring tool built in 6 weeks. Here's how I did it. The Problem Existing monitoring tools are either too expensive ($75-100/mo) or have outdated UIs. I wanted something affordable for side projects with modern tech. Tech Stack Backend: FastAPI (Python) Celery + Beat for background workers Redis as message broker SQLAlchemy ORM PostgreSQL Frontend: Next.js 14 (App Router) TypeScript Tailwind CSS Zustand for state Deployment: Railway (backend + worker) Vercel (frontend) Key Features Real-time health checks (30s - 5min intervals) Multi-channel alerts (Email, Slack, Telegram, Discord, Webhooks) Response time tracking Public status pages Payment integration (LemonSqueezy) Technical Challenges 1. Celery + Beat in One Process Railway needed combined worker+scheduler: python celery -A app.celery_app worker --beat --concurrency=2 2. Multi-Channel Alerts Created abstraction in alerts.py for 5 different APIs. 3. Token Refresh Axios interceptor hand