banklab

Overview ¶

Package banklab is BankLab, a retail bank's API: customers with current and savings accounts, transaction history, monthly statements, transfers and bill payments that take an Idempotency-Key, and a reconciliation check. It is the reference app for the fintech pack. Bill payments go to the bank's own biller accounts: nothing leaves the app, and no payment provider is involved.

Planted bottlenecks (see README.md), each switched off by a fix flag:

• lock: every transfer and payment holds one ledger-wide lock, fraud check included, so money moves one transfer at a time and balance reads queue behind it (fix "lock" runs the fraud check first and locks only the two accounts involved).
• balance: an account's balance is the sum of all its postings, recomputed for every balance read and every transfer, so it slows down as history grows (fix "balance" keeps a running balance).
• statements: a monthly statement scans the whole bank's journal for the account's postings (fix "statements" reads the account's own postings, found by date).