Building Multi-tenant SaaS Backends with Prisma

Multi-tenancy is the ability to serve multiple customers (tenants) from a single database while keeping their data strictly isolated.

1. The Strategy: Column-based Isolation

Every table in your database includes a tenantId column. This is the most cost-effective way to scale.

2. Prisma Middleware

Use Prisma middleware to automatically inject the tenantId into every query, preventing one customer from accidentally seeing another's data.

prisma.$use(async (params, next) => {
  if (params.model === "User") {
    params.args.where = { ...params.args.where, tenantId: currentTenantId };
  }
  return next(params);
});

3. Row Level Security (RLS)

If you're using PostgreSQL, combine Prisma with Row Level Security for a truly unbreakable isolation layer at the database level.

Building a SaaS is about building Trust, and architecture is where that trust begins.