Legacy System Migration for Capital Markets Firms

Legacy systems hold the books and records, settlement instructions, positions and reporting that a capital markets firm relies on every day. They are accurate and trusted, but they are also slow, hard to extend and increasingly expensive to maintain. Replacing them is rarely a question of whether, but of how to do it without interrupting the business that depends on them.

The risk that keeps these projects postponed is not the new software itself. It is the transition. Data must move without loss, integrations to banks, custodians and market infrastructure must keep working, and daily processes must continue without disruption. A failed cutover can affect client service, so firms delay until the risk feels manageable.

I manage that transition. The approach is parallel running: the new system is built alongside the old one, populated with the same data, and connected to the same counterparties. Both systems operate together for a defined period, so outputs can be compared, differences reconciled and confidence built before any switch is made. Nothing is removed until the new system has proved itself under real conditions.

The work covers the software build, the data migration, the rebuild of integrations and the testing that ties them together. Senior management sets the priorities and approves each stage, and I handle the technical delivery behind them. After migration, I remain available for maintenance, fixes, new development and further integrations when requested.

The result is a migration that does not ask the firm to choose between modernisation and continuity. The old and new systems run together first, the evidence is gathered, and the switch happens only when the new system is ready.