The brief
Every flat runs on some combination of a group chat, a shared spreadsheet, and someone's memory. That works right up until it doesn't — a bill gets missed, someone moves out mid-month, or a housemate quietly stops doing their share of the chores. Flatly's founders wanted to build the tool that replaces all of that with a single, calm shared surface.
The rules were clear: it had to feel warm, not like a fintech product; it had to work on both iOS and Android without a compromise on either; and the infrastructure had to be reproducible from day one, because they knew they'd be iterating fast.
What we designed
The visual language was the first decision. Bills, rent and money are stressful; the app couldn't add to that. We built a warm palette, friendly typography, and generous rhythm — the app looks more like a household ritual than a payment product. Housemate avatars anchor every screen so the flat always feels present, not abstract.
The core loop is: create a household, add members, add recurring bills, and let the app surface what's due next. Tasks and expenses share the same household model, so 'who owes what' and 'whose turn is it' answer to the same source of truth.
What we built
- Full cross-platform Flutter app (iOS + Android) with Riverpod for state management.
- Household setup with member avatars, roles and invitations.
- Recurring bills with due-soon surfacing and split logic per household.
- Task lists and an expenses ledger sharing the same household model.
- TypeScript services on AWS, defined in CDK — reproducible dev, staging, prod environments from day one.
- MongoDB for the household data model; payments integration wired for the settlement roadmap.
Stack and infrastructure
Flutter with Riverpod gave us pixel-identical UI on both platforms and predictable state for a data model that touches almost every screen. On the backend, we shipped TypeScript services running on AWS, defined entirely in CDK — meaning any environment can be torn down and rebuilt from source, and every infrastructure change is code-reviewed like any other PR.
Outcome
Flatly is in closed beta with real flats in New Zealand. The bill-splitting and task assignment flows are validated end-to-end. The roadmap is now on the harder half of the problem — actually settling money between housemates — with the payments integration already wired in and the infrastructure ready to carry it.