Architecting a multi-tenant B2B SaaS application requires balancing two opposing forces: operational cost efficiency and rigorous tenant data isolation. Provisioning an isolated database for every enterprise client becomes financially unsustainable as tenant volume grows; conversely, storing all tenant data in a single shared database without cryptographic isolation introduces severe data leak liabilities.
The Multi-Tenancy Architecture Spectrum
In our Launch Studio production builds (/services/launch-studio/mvp-build), we adopt a pooled-database model powered by PostgreSQL Row-Level Security (RLS). Every table contains an indexed tenant_id column, and database connection pools enforce cryptographic tenant boundaries at the database engine level.
Implementing Non-Bypassable Row-Level Security (RLS)
Application-level filtering (such as adding WHERE tenant_id = current_tenant in ORM queries) is fragile: a single omitted WHERE clause in a junior developer’s PR exposes customer data across accounts. PostgreSQL RLS resolves this by enforcing policies at the database kernel level.
Injecting Tenant Context via JWT Claims
When a user authenticates, Supabase Auth issues a cryptographically signed JWT containing their verified app_metadata.tenant_id. In PostgreSQL, RLS policies read this context directly using auth.jwt() ->> "tenant_id", automatically scoping all SELECT, INSERT, UPDATE, and DELETE operations without requiring manual application filtering.
Dynamic Custom Domain Routing with Next.js Middleware
Enterprise clients demand dedicated custom domains (such as app.acme-corp.com) rather than generic shared subdomains. Using Next.js Edge Middleware, our routing layer extracts the incoming request hostname, verifies custom domain ownership against a Redis edge cache in sub-5ms, and rewrites the internal request path to the appropriate tenant tenantId route without manual DNS intervention.
Architectural Guarantee: Enforcing tenant isolation at the PostgreSQL database kernel layer guarantees zero data bleed across accounts, satisfying SOC 2 Type II audit requirements without requiring dedicated infrastructure overhead.