Money systems layer
Ledgers and payments
Build a ledger that can't create or lose money, and prove it.
- 01
Double-entry bookkeeping for engineers
Every movement has two sides that sum to zero.
- 02
Money in code
Integers, minor units, rounding and currency.
- 03
Balances are derived
Store movements, compute balances.
- 04
Idempotent transfers
Charge once, even when the client retries.
- 05
Webhooks that lie
Late, duplicated and out-of-order callbacks from banks.
- 06
Reconciliation
Matching your records to the bank's, every day.
- 07
Settlement
When money has really moved.
- 08
ISO 20022
The message format banks are moving to.