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Existing monitoring tools are either too expensive ($75-100/mo) or have outdated UIs.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 handles JWT expiry smoothly.

Results

• 34 API endpoints
• 5 alert channels
• Full payment system
• Open source (MIT)

Live Demo
![ ](https://dev-to-uploads.s3.amazonaws.com/uploads/articles/ow88ql588cpko5rs7jub.png)

• Website: [https://checkapi.io](https://checkapi.io )
• GitHub: [https://github.com/JEONSEWON/api-health-monitor]
Built with AI assistance (OpenClaw) which sped up development significantly.

Questions? Ask in comments!

#buildinpublic #indiehacker