Three loan systems, one ledger, zero downtime during cutover
A ₹4,000 crore book was running across three systems bought at different times. Origination did not talk to servicing, collections worked off a nightly export, and month-end close took eleven days because finance was reconciling by hand. The auditor had flagged the manual journal entries two years running.
Rebuilt the core on a single double-entry ledger with maker-checker on every write. Migrated 1.1 million loan accounts in eight tranches over four weekends, running old and new in parallel with automated reconciliation between them until the numbers matched to the paisa. Cutover happened without a business day of downtime.