This article discusses the challenges of ensuring consistency in systems that use separate databases for transactions and master data. It highlights the "Write Last, Read First" principle to manage operations across these systems, emphasizing the importance of designating a system of record and ensuring idempotency in operations.

Maintaining consistency in a system comprised of separate databases can be challenging, particularly in the absence of transactions. The article discusses the importance of defining a system of record versus a system of reference and emphasizes the Write Last, Read First principle to ensure safety properties like consistency and traceability in financial transactions.