Marea, cycle-based finances for couples
An app for tracking a couple's expenses by half-month or by month, synced between two phones, that works offline and costs zero in the cloud.
- My role
- Full design and development
- Year
- 2026
- Technologies
- JavaScript, Service Worker, Cloudflare Pages Functions, Cloudflare D1, PWA
The challenge
Two people log expenses at the same time from different phones, sometimes with no signal, and no write can be lost or overwrite the other's. It also had to be secure and cost nothing per month.
The solution
Each transaction is its own row in the database, and changes sync through a cursor that never loses a write. When offline, changes wait in a queue and are sent once the signal is back, with undo and a 30-day trash. Access is protected with constant-time comparison, lockout after failed attempts and single-use invitations that expire in 24 hours.
It started as a personal tool and became a full app that runs on Cloudflare’s free plan.