Ledgerly: splitting rent without the spreadsheet

The problem

My flat tracked shared costs in a Google Sheet. Nobody updated it, and every month ended with an awkward conversation about who owed what.

Constraints

• Must work on cheap Android phones over slow data.
• No app install. Flatmates would not download another app.
• Zero hosting budget beyond free tiers.

Architecture

1. Next.js UI
2. →tRPC API
3. →Postgres (Neon)
4. →UPI deep link

Key decisions

tRPC over REST. One developer, one codebase. End-to-end types removed a whole class of bugs and I didn't need a public API.

Store balances as a ledger, not totals. Every expense is an immutable row, and balances are computed. This made "undo" and history trivial.

Results

What I'd do differently

Add offline support from day one. Most bills get logged at the shop counter, where the signal is worst.