Building Multi-Tenant SaaS with Next.js 16, NestJS 11, and PostgreSQL RLS

A developer details building Äbasto, a B2B SaaS for inventory and POS management, using a monorepo with Next.js 16, NestJS 11, and PostgreSQL. Row-Level Security (RLS) enforces data isolation at the database level, with NestJS injecting tenant context via SET LOCAL commands. The approach reduces human error by delegating access control to PostgreSQL rather than relying solely on application-level WHERE clauses.