Building a SaaS from Scratch with Next.js + Stripe

Every SaaS needs the same foundation: authentication, multi-tenancy, subscription billing, and a way for customers to manage their own plan. Here's the architecture we reach for when starting a new SaaS with Next.js and Stripe.

1. Multi-tenancy model

For most early-stage SaaS products, a shared database with a tenant_id (or organization_id) column on every table is simpler to build and operate than separate databases per customer. Enforce tenant isolation at the query layer — ideally with row-level security in PostgreSQL — so a bug in application code can't leak data across tenants.

2. Authentication and organizations

Model users and organizations as separate entities from day one, even if you launch with one user per org. This avoids a painful migration later when customers inevitably ask for team seats. A users table, an organizations table, and a memberships join table with a role column covers almost every case.

3. Stripe billing

• Create a Stripe Customer for each organization, not each user.
• Use Stripe Checkout for the initial subscription — it handles tax, payment methods, and 3D Secure for you.
• Use the Customer Portal for plan changes, payment method updates, and cancellations instead of building your own.
• Sync subscription status via webhooks (checkout.session.completed, customer.subscription.updated/deleted) into your database — never trust client-side state for entitlements.

4. Feature gating

Store the current plan and its limits in your database, updated by the webhook handler. Gate features by reading from your database, not by calling Stripe on every request — that adds latency and a hard dependency on Stripe's uptime for your core app.

Get these four pieces right and everything else — onboarding flows, usage dashboards, team management — builds naturally on top. Most SaaS rewrites we've seen happen because multi-tenancy or billing was bolted on after the fact rather than designed in from the start.