Several international markets — some with fairly complex tax workflows — were running live, invoice-level tax computation (9M+ monthly transactions) on an older platform. Moving them onto modernized infrastructure wasn't just a lift-and-shift: the existing workflows had known rounding and calculation-accuracy issues that needed to be resolved in the process, in a domain with zero tolerance for errors.
I led the end-to-end migration of these live tax workflows onto modernized infrastructure, and in doing so reduced rounding issues and increased calculation accuracy across the affected markets — the priority was correctness, not just replicating the old behavior on new infrastructure. Because the workflows touched systems and teams outside my own, a large part of the work was driving cross-team investigations to unblock issues and bring the migration to closure without customer-facing disruption.