Best Tools for Multi-Tenant SaaS Architecture
One codebase, many customers, data fully isolated — the stack that makes it work
Multi-tenancy is where most SaaS MVPs cut corners and pay for it later. I've built BookBed (booking SaaS, multiple property owners) and Callidus (clinic SaaS, multiple practices) with proper row-level data isolation from day one. These are the tools that make that practical.
Postgres RLS policies enforce tenant isolation at the database level
RLS is the architectural decision that makes multi-tenancy safe. Instead of adding `WHERE tenant_id = ?` to every query and hoping nothing slips through, you write a policy once and the database enforces it everywhere. Supabase makes enabling and testing RLS policies straightforward. This is the foundation.
Per-tenant subscription billing with customer + subscription objects
Model each tenant as a Stripe Customer with their own Subscription. Store the Stripe customer ID and subscription status in your tenants table. Use webhooks to keep subscription state in sync — never trust client-side Stripe data for access control. This pattern scales cleanly from 10 tenants to 10,000.
Server components + middleware for per-tenant routing and auth
Next.js middleware is the right place to handle tenant identification — read the session JWT, extract the tenant ID, pass it down via headers or context. Server components can then query Supabase with the correct auth context. This keeps tenant logic out of every component.
Per-tenant transactional email with sender domain customisation
Multi-tenant SaaS often needs to send email on behalf of tenants — booking confirmations from a property owner's brand, order receipts from a restaurant. Resend's domain management API lets you verify per-tenant sending domains programmatically. This is the detail most SaaS MVPs skip and regret.
Wildcard subdomain support for per-tenant custom domains
Vercel's wildcard domain handling (`*.yoursaas.com`) plus their middleware make per-tenant subdomains straightforward. For SaaS products that want each customer on `customer.yoursaas.com`, this is the lowest-friction deployment path. Custom apex domains require additional DNS verification logic — plan for it.
The minimal multi-tenant SaaS stack: Supabase (RLS for isolation) + Stripe (per-customer subscriptions) + Next.js (middleware for tenant context) + Resend (transactional email) + Vercel (subdomain routing). Get the RLS policies right in week one — retrofitting them onto an existing schema is painful.