After using Farcaster for a year, I noticed the platform lacked a reminder system like Reddit’s RemindMeBot. I built @alertme - mention it with a time (“@alertme in 2 hours”) and it replies when the time comes.
Technical Implementation
Stack: TypeScript, Express, PostgreSQL, Railway
External APIs: Neynar (Farcaster webhooks), Warpcast (casting replies)
The architecture handles:
- Webhook processing - Neynar fires webhooks when @alertme is mentioned
- Natural language time parsing - Using
chrono-nodeto interpret “2 hours”, “10 days”, “tomorrow” - Scheduled reminders - Cron job checks database every 5 minutes for due reminders
- Rate limiting - 1-second delays between replies to avoid API throttling
Interesting Challenges
DM API Restrictions: Warpcast restricts DM API access to established accounts. After testing permissions across multiple accounts, I pivoted to public replies instead - which actually improved UX through social proof.
Time Parsing Edge Cases: Users write times inconsistently (“2 hours” vs “in 2 hours”). Added text normalization to handle common patterns before parsing.
Production Deployment: First time using Railway for deployment. Learned about environment variable management across services and container restart behavior.
Try It
Use @alertme on Farcaster or join Farcaster with my referral.
Built in November 2025. Monitoring usage to determine future feature additions.