Multi-tenancy at the architecture level, not the configuration level, from day one.
Tenant isolation is an engineering problem; a mis-scoped query must be structurally impossible, not merely unlikely.
Rationale: In fintech, tenant isolation is an engineering problem; a mis-scoped query must be structurally impossible, not merely unlikely.
Trade-off accepted: Heavier upfront data-model and access design, slower first sprint, faster every sprint after.