Event-Driven Patterns for Cloud-Native Banking: Lessons from What Works and What Hurts

A practitioner's account of applying event-driven architecture in a regulated banking environment at Investec. Covers core concepts (events vs. commands, EDA vs. event sourcing), the real benefits in banking (decoupling payment flows, fan-out, audit trails, fault tolerance), and the hard lessons: the six-month ramp-up for new engineers, the necessity of outbox/inbox patterns to prevent lost or duplicate events, treating event contracts as permanent public APIs, and handling event ordering explicitly or implicitly. Emphasizes that success requires organizational investment—shared developer platforms, paved paths, and hands-on training—not just the right technology.