Hackathon Stopwatch

What it is

A single-purpose site for a hackathon day: a public page shows a count-up clock that an admin starts, pauses and resets from a phone. Time is server state in Supabase, mirrored to every viewer through Realtime with a polling fallback.

The problem

A livestreamed hackathon needed one authoritative clock that organizers could control remotely.

How it works

1. One Supabase row holds status, accumulated_ms and started_at; elapsed time is derived and nothing is written while the clock runs
2. RLS grants the browser SELECT only; every write goes through a Vercel Function holding a server-only key
3. scrypt password check with rate limiting, HMAC-signed HttpOnly session cookie, CSRF token and a strict CSP
4. Vanilla JS with vendored supabase-js and per-client clock-skew correction

Stack

Disciplines

For your business

Small real-time tools with proper security, built and deployed in a day.