Processing, settlement reconciliation and biometric authentication for a payment services provider.
A mission-critical platform nobody wanted to touch: settlements reconciled by hand, transaction reports assembled in spreadsheets, and a compliance audit on the calendar.
Rebuilt reconciliation as a nightly pipeline over Oracle and SQL Server with every mismatch surfaced, not summarised.
Designed the biometric authentication service against the PCI-DSS controls it had to pass.
Modernised the core incrementally — strangler pattern, no big-bang release.
Reconciliation went from a day of manual work to a report waiting in the morning. The audit passed on the first pass.