Multi-Tenant SaaS Architecture in Next.js

If your SaaS serves teams or organizations, you're building a multi-tenant app — many customers sharing one deployment while their data stays separate. Getting the model right early prevents painful migrations later.

Shared database, scoped rows

The most common approach: one database where every tenant-owned row carries a `tenantId` (or `organizationId`). It's simple, cheap, and scales well — but it puts the burden on you to scope every single query. Miss one, and a customer sees another's data.

Isolated databases

For strict compliance needs, you can give each tenant their own database or schema. This maximizes isolation but multiplies operational overhead — migrations, backups, and connections all scale with your customer count. Most startups don't need this until enterprise deals demand it.

Scope every query, no exceptions

• Derive the current tenant from the session, never from client input.
• Put tenant scoping in your data layer so it's applied consistently, not per-component.
• Add database constraints and tests that fail loudly if a query forgets the tenant filter.
• Log and alert on any cross-tenant access attempt.

Routing tenants

You can identify tenants by subdomain, path prefix, or purely from the logged-in user. Subdomains feel premium and help with branding; a shared domain is simpler to operate. Choose based on your customers' expectations.

KitCraft's SaaS templates put data access behind a typed layer where tenant scoping lives in one place — the right foundation to grow a multi-tenant product safely.