The dual-write problem appears whenever a system must write to two services (such as a database and an authorization engine) and cannot guarantee atomicity across them. A crash at the wrong moment can leave your system inconsistent, even if each component works perfectly. This talk explains why dual writes are fundamentally unsafe within a single process and what architects can do about it. We’ll explore practical patterns used in real-world distributed systems: - Out-of-band reconciliation - Making a single system the source of truth - Event sourcing - CQRS - Durable execution frameworks like Temporal, and - Transactional outbox designs. Attendees will learn how to identify dual writes in their own architectures and choose the right mitigation strategy based on scale, consistency needs, and team maturity. This session gives engineers clear mental models and actionable tools for building reliable multi-service systems.