02/09/2026
The database layer is one of the least visible components in a financial system, but one of the most consequential. Misconfigure it and the failure modes are concrete: duplicate transactions, inconsistent balances, audit gaps, and outages that regulators classify as operational risk events under DORA.
For most mid-sized banks and payment processors, PostgreSQL remains the correct default — mature, fully ACID-compliant, and operationally well-understood. The case for distributed SQL (CockroachDB, YugabyteDB) is specific: high write volumes approaching single-node limits, multi-region active-active availability, or data residency obligations under PSD3. NoSQL has a legitimate role, but only in bounded, non-transactional contexts — session state, fraud signal caching, read-optimised reporting. The discipline is ensuring it never touches ledger data.
https://oceanobe.com/news/database-architecture-for-financial-applications/1943