Developer uses PostgreSQL Row Level Security to enforce multi-tenant isolation in Next.js

A developer building multi-tenant SaaS applications found that relying solely on application-level checks for tenant isolation placed too much responsibility on the codebase. To address this, they implemented PostgreSQL Row Level Security (RLS) as an additional enforcement layer at the database level, alongside server-side authorization. The architecture ties users to organizations, with roles such as Owner, Admin, and Member controlling access permissions across the application. The approach also covers related features including team invitations, API keys, usage limits, and organization-based billing. The developer packaged these patterns into a reusable B2B SaaS foundation built on Next.js and Supabase, concluding that multi-tenancy is fundamentally an authorization model requiring consistency across both application and database layers.