nivomoney

A neobank demo in Go: identity, wallets, transactions, risk and a double-entry ledger, each its own service, with React apps on the front. All data is synthetic.

Eight services and a gateway. Decisions are written up as ADRs.

why it exists

Tutorials stop at one service and one database. Money integrity, audit trails and fraud limits sit past that point.

nivomoney was built to go there: the core systems of a bank, small enough to follow.

what it taught

The source lays out a bank's parts: where service boundaries fall, how a double-entry ledger works, what moving money across services asks for.

A balance rule belongs in the database. Postgres refuses to post an entry of 100 against 90.

The wiring from transfers to that ledger is where the demo stopped.