THE FINTECH BUILDER · SYNTHETIC BANK BOOKS

An atomic reversal and replacement

Derive an exact inverse, inspect a valid replacement, and observe the one boundary that changes committed balances.

USD minor units (cents). Customer deposits are bank liabilities. Original history stays unchanged.

The correction visibility boundaryThe original remains preserved. Both new journals are candidates until one successful atomic commit.Original preservedAccepted wrong2500Inverse + replacement + linkCandidates remain private

Original accepted legs

Isolated candidate · not a separate commit

Committed journal audit

SeqJournal / legSideCents

Candidate inverse and replacement share a single visible operation. A rejected replacement leaves both absent. This lab executes the portable reference; actual database durability and concurrent transactions are tested separately.