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Immutable transaction log
ID MOD-002
System SD01
Repo bank-core
Build status Deployed
Deployed Yes
Last commit 35402a8a7d9c6f1e2b5c8d0e4f7a3b6c9d2e5f8a

Every ledger entry is append-only. No record can be modified or deleted. Corrections are made via reversal entries, not edits. Full event-sourced history retained for 7 years.

Module dependencies

Depends on

Module Title Required? Contract Reason
MOD-001 Double-entry posting engine Required — Appends every ledger posting to the immutable log — requires MOD-001 to emit postings.
MOD-104 AWS shared infrastructure bootstrap Required — AWS shared infrastructure provisioned by MOD-104 (EventBridge buses, S3, KMS, Kinesis, Cognito) is required before this module can be deployed.
MOD-103 Neon database platform bootstrap Required — Neon database and schema provisioned by MOD-103 must exist before this module can read or write Postgres.

Required by

Module Title As Contract
MOD-003 Real-time balance engine Hard dependency —
MOD-004 Multi-currency ledger (NZD/AUD) Hard dependency —
MOD-005 Daily accrual calculator Hard dependency —
MOD-007 Account state machine Hard dependency —
MOD-008 Dormancy & escheatment engine Hard dependency —
MOD-016 Rule-based typology engine Hard dependency —
MOD-021 Payment limit & velocity controller Hard dependency —
MOD-070 Transaction history & search Hard dependency —
MOD-113 Statement generation Hard dependency —

Policies satisfied

Policy Title Mode How
GOV-006 Internal Audit Policy LOG Internal audit has immutable access to all financial transactions — no data can be altered post-audit
REP-005 Data Quality & Assurance Policy LOG Data lineage from source transaction to regulatory submission is fully traceable
AML-005 Transaction Monitoring Policy LOG Transaction history for monitoring is immutable — cannot be suppressed or modified
PAY-002 Settlement Risk Policy LOG Settlement records are permanent — provides legal certainty for all payment obligations
PAY-007 Ledger Posting & Account Integrity Policy LOG Immutable transaction log provides the authoritative record of all payment events — cannot be altered or suppressed after posting.

Capabilities satisfied

Capability Title Mode How
CAP-001 NZ bank account (NZD) AUTO Every NZD posting creates and maintains the account balance — account existence is defined by the ledger.
CAP-002 AU bank account (AUD) AUTO AUD denominated postings are stored in the immutable log with the same guarantees as NZD.
CAP-003 Multi-currency wallet (USD, EUR, GBP, SGD, JPY) AUTO Foreign currency transactions are logged in both base and foreign currency, providing the permanent record for multi-currency wallet balances.
CAP-018 Shared accounts & joint authorisation AUTO Records all transactions against a shared account with the authorising signatory identity captured on each posting — joint account history is fully traceable to the individual who initiated each entry.

Part of SD01 — Core Banking Platform Compiled 2026-05-22 from source/entities/modules/MOD-002.yaml