Aaron Perkelprojects / lejer
Shared bills for the people you live with
Lejer is a free bill-splitting app for people who share a lease. Someone posts each house bill with its statement; everyone sees their share, gets a reminder before it’s due, and checks off when they’ve paid — whether one person pays everything or each bill has its own owner who fronts it. It grew out of a PHP dashboard my roommates and I used, and two households moved onto it at launch.
Postgres row-level security per household. Each request runs in a transaction that sets the household with set_config(…, true), and every policy reads it. The app connects as a role without BYPASSRLS — the migration refuses to run otherwise — and the owner role is confined to four listed call sites.
Email sign-in codes: six digits from a CSPRNG, stored only as a SHA-256 hash, 10-minute expiry, dead after five wrong guesses, and compared in constant time. Rate limits per email, per (hashed) IP, and a global daily cap. Sessions are a signed JWT in an httpOnly cookie, 30 days with sliding renewal.
An hourly Vercel Cron tick sends each household’s reminders at its own local send hour; a Vercel Queues topic handles delayed wake-ups. 14 React Email templates.
Statements live in a private Blob store and are served only through an authenticated route; documents upload straight from the browser.
18 hand-written SQL migrations with a small runner. Both legacy households were imported from the old app’s database in a single transaction at launch.
14 verification suites (~790 checks) run against a Neon dev branch: RLS isolation, identity, bills, cron, the import, and HTTP.
The operator console reads only through SECURITY DEFINER functions that never return dollar amounts.