Guides
How to Build a SaaS Application With Next.js
Before any product-specific feature, a SaaS application needs three things working correctly: accounts, a way to keep customer data isolated, and billing. This covers the architecture decisions behind each.
Prerequisites
- arrow_rightA Next.js project with a database (Postgres/Supabase)
- arrow_rightA Stripe account for billing
Step 1: Design for Multi-Tenancy
The simplest and most common approach: a shared database with an organization_id (tenant ID) column on every table that holds customer data, enforced on every single query — either manually or via row-level security if using Postgres/Supabase.
create table tasks (
id uuid primary key default gen_random_uuid(),
organization_id uuid not null references organizations(id),
title text not null
);Step 2: Wire Up Subscription Billing
Create a Stripe Customer and Subscription when an organization signs up for a paid plan, and store the subscription status on the organization record, updated via Stripe webhooks (not the checkout redirect) whenever it changes.
Step 3: Gate Features by Plan
Check the organization's current plan (read from your database, kept in sync via webhooks) before rendering or allowing access to plan-gated features, both in the UI and at the API level.
Common Errors
- arrow_rightA query missing the organization_id filter, leaking data across tenants — this is the single most consequential bug category in a multi-tenant app and worth extra review attention
- arrow_rightSubscription status going stale because it's only updated via the checkout redirect, not webhooks
- arrow_rightFeature gates checked only in the UI, letting a determined user hit the API directly and bypass the plan restriction
Security Considerations
- arrow_rightEvery query touching tenant data must filter by organization_id — consider row-level security as a database-enforced backstop rather than relying solely on application code discipline
- arrow_rightVerify Stripe webhook signatures before trusting any billing event
- arrow_rightDon't expose another organization's data in API error messages
Frequently Asked Questions
Should each customer get a separate database?add
For most SaaS products, no — a shared database with a tenant ID column is simpler to operate and sufficient until you reach a scale or compliance requirement that specifically demands isolation, which is a smaller set of cases than commonly assumed.
How do I keep subscription status accurate?add
Update it from Stripe webhook events (subscription created, updated, canceled), not from the checkout success redirect alone — the redirect can be missed if the customer closes the tab early.
What's the biggest risk in multi-tenant architecture?add
A query that forgets to filter by tenant ID, which can leak one customer's data to another — this is worth specific code review attention and, where the database supports it, a row-level security policy as a backstop.