Tech lead on the re-platform of the forex system behind Visa's Currency Cloud.

Visa had acquired Currency Cloud, and with it a foreign-exchange system built on legacy Ruby. It handles over $250 million a day in financial transactions.

The brief was to modernise it. Move off Ruby onto an Express and Next.js setup so the application could be scaled more effectively, and modernise the UI and the processes around it. We came in as tech lead in January 2023 and ran it to June.

You do not pause a system that settles a quarter of a billion dollars a day. Every migration step had to be reversible, observable, and invisible to the businesses transacting through it, all inside the compliance perimeter of a global payments company.

We led the migration from the legacy Ruby stack to Express and Next.js. TypeScript throughout, Jest for the safety net, Azure and Jenkins carrying the pipeline. The UI and the surrounding processes were modernised as part of the same programme.

We held the tech lead role for six months on a programme with a target architecture and a live system underneath it. That is what this page claims.

We do not have an end state to report. A re-platform of that size runs longer than one contract, and we would rather say so than describe a finish we were not there for.