Building a cross-domain temporal backbone that actually works in Financial Services. Financial Services firms often build robust SCD2 history within individual domains, yet still fail when asked to reconstruct cross-domain state at a point in time. This article explains why single-domain SCD2 is insufficient and sets out a practical design for a multi-domain temporal backbone spanning Customer, Account, Party, Product, Contract, and Transactions. It shows how to align entity history, temporal relationships, and bi-temporal transactional facts to support defensible point-in-time analysis across risk, conduct, AML, remediation, and regulatory use cases.