Direct Debit Migration
Migration of a legacy payment platform toward an event-driven microservices architecture.
Problem
A legacy Direct Debit platform limited scalability and made changes risky. It needed to scale and evolve without disrupting live payment flows.
Architecture
Incremental decomposition of the monolith into event-driven services, with events as the integration contract and the legacy system strangled over time.
Technical challenges
Migrating a live, money-moving system with zero tolerance for lost transactions while both old and new paths ran in parallel.
Solution
A strangler-fig migration: route traffic gradually, verify parity through events, and decommission legacy components only after confidence was established.
Scale
Restructured a core payment platform for higher throughput and reliability.
Lessons learned
Events made the migration observable and reversible. Incremental cutover beat any big-bang rewrite for a system that could not go down.
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