PostgreSQL Row-Level Security for Multi-Tenant SaaS

--- title: "PostgreSQL RLS: Your Last Defense Against Tenant Data Leaks" published: true description: "Learn how PostgreSQL Row-Level Security prevents tenant data leaks in multi-tenant SaaS, with policy patterns, index strategies, and benchmarks at 10K tenants." tags: postgresql, architecture, security, api canonical_url: https://blog.mvpfactory.co/postgresql-rls-your-last-defense-against-tenant-data-leaks --- ## What We Will Build In this workshop, we will set up PostgreSQL Row-Level Security (RLS) for a multi-tenant SaaS application. By the end, you will have tenant isolation enforced at the database layer — so one tenant literally cannot read another's data, even when your application code has bugs. Let me show you a pattern I use in every project that handles multi-tenant data. ## Prerequisites - PostgreSQL 15+ - A Kotlin backend (Ktor or Spring Boot) — the SQL patterns apply to any stack - Basic familiarity with SQL policies and indexing ## Step 1: Understand Why Application-Laye