Bank8:Ledger — the core ledger

The system of record for money positions: accounts, products, double-entry postings, balances, schedules, and the full configuration library (parameters, flags, restrictions, calendars, plans, contracts) that drive them. 91 endpoints, 44 tables, one schema the service owns exclusively.

Use cases

Retail & business banking

• Account opening — products compose validation modules (limits, overdraft rules, sweeps, tiered rates); parameters resolve through the hierarchy (global → product → account) so a product change never needs data migration.
• Transfers — a transfer is one POST /v1/postings call with a batch and a single instruction; retries with the same idempotency_key are safe by construction.
• Scheduled postings — due schedules generate posting batches in one transaction per batch (recurring fees, sweeps, interest).

Finance operations

• Balance truth — live and end-of-day balances per denomination; every posting batch is balance-validated before any row is written (422 on imbalance, never compensating entries after the fact).
• Statement generation — scheduled generation writes documents to platform storage; regeneration is a per-account-period workflow.
• Config library — flags, restrictions, plans, contract modules: the whole product rule set is data, unit-testable without a DB.

API surface (91 endpoints, selected families)

Family	Endpoints	Scope
Accounts	GET/POST /v1/accounts, …/{id}, …/balances, …/transactions, …/statements	bank8:ledger:accounts:read/write
Products	GET/POST /v1/products, …/{id}/activate, versions	bank8:ledger:products:*
Postings	POST /v1/postings, POST /v1/postings/async, GET …/{id}, republish	bank8:ledger:postings:read/write
Balances v2	GET /v2/balances/{live,end,series}	bank8:ledger:balances:read
Schedules	GET/POST /v1/schedules, tags, associations	bank8:ledger:schedules:*
Customers	GET/POST /v1/customers, link-auth	bank8:ledger:customers:write
Parameters	/v1/parameters, viewEffective, derived values	bank8:ledger:parameters:*

Invariants

• Money is rust_decimal end-to-end; the JSON wire format is a string.
• Postings are idempotent per (env_id, idempotency_key) — partial unique index + ON CONFLICT.
• Audit + outbox inserts propagate errors inside the posting transaction: a posting whose audit/event write fails never commits.

Full documentation

The complete detail lives in this product's sub-pages:

• Architecture (DDD) — the full document, harvested from the unit's repository at build time.
• Business rules (BRD) — the full document, harvested from the unit's repository at build time.
• Security — the full document, harvested from the unit's repository at build time.
• Overview (repo README) — the maintainer's README in the consolidated reference section.