PostgreSQL Row-Level Security: Multi-Tenancy Without Leaking Tenant Data

Building a multi-tenant SaaS application is fraught with danger. In a traditional shared-database architecture, every single SQL query must remember to append a tenant filter: SELECT * FROM invoices WHERE tenant_id = 'acme_corp'; If a developer writes just one query and forgets WHERE tenant_id = :id: SELECT * FROM invoices WHERE id = :invoice_id; -- BUG! Tenant Acme Corp can suddenly view Tenant Globex's financial invoices! This is one of the most common and catastrophic data leak vulnerabilities in SaaS platforms. Instead of relying on fragile application-level WHERE clauses, PostgreSQL provi