Build a Multi-Tenant Saas API with NestJS and Postgres

A step-by-step guide to building a multi-tenant SaaS task management API using NestJS, PostgreSQL Row-Level Security (RLS), and TypeORM. The tutorial covers setting up RLS policies that automatically filter data by tenant at the database level, extracting tenant context from JWT tokens via middleware, using QueryRunner with transaction-scoped session variables to propagate tenant IDs through async Node.js operations, and verifying that cross-tenant data access is blocked even when task IDs are known. The approach enforces isolation at the database layer rather than relying solely on application code, reducing the risk of accidental data leaks.