One application, a thousand customers
How modern SaaS products serve multiple customers with a single codebase.
When you build a SaaS, you don’t want to run a separate server or database for every customer. That’s expensive, complex and unscalable. The solution? Multi-tenant architecture — one application that serves hundreds or thousands of customers simultaneously, while keeping everyone’s data completely separated.
What is multi-tenancy?
The basics explained.
A tenant is a customer or organisation that uses your software. With multi-tenancy, all tenants share the same application, but each tenant only sees their own data.
Think of Gmail: millions of users share the same application, but nobody can see anyone else’s emails. That’s multi-tenancy in action.
The three approaches
Each strategy has its pros and cons.
Shared database, shared tables
All tenants in the same database and tables. A tenant_id column separates the data. Cheap and simple, but requires discipline to prevent data leakage.
Shared database, separate schemas
One database, but each tenant has their own set of tables. Better isolation, slightly more complex to manage.
Separate databases per tenant
Maximum isolation and security. But more expensive and harder to scale. Usually only for enterprise customers.
Most SaaS startups choose option 1 — it’s by far the most cost-effective and scales well with Row Level Security (RLS) in PostgreSQL.
Build once, scale endlessly
Multi-tenant architecture is the backbone of every successful SaaS. It enables you to serve thousands of customers with a single codebase, while keeping everyone’s data safely separated. Start simple with shared tables and grow from there.