Multi-tenant and RLS: simple definition for a B2B SaaS

In brief

RLS (Row Level Security) is a database mechanism that limits the rows a user can see, at the server level: each client of a SaaS only sees their own data, whatever they do. It's the standard way to isolate your clients' data in a multi-tenant application.

• Isolation is structural: applied by the database, not by the application code.
• Every query automatically checks the rights; impossible to bypass through the API.
• Compatible with PostgreSQL, notably on Supabase.
• GDPR compliant: each client remains strictly isolated.

The problem, concretely

In a B2B SaaS, several clients share the same database. Without strict isolation, a client could see another client's data by accident or manipulation. Secure multi-tenant answers this risk: RLS applies isolation at the database level, a structural guarantee, not a promise from the code.

How it works

Each table row carries the tenant (client) identifier. An RLS policy checks that the user belongs to that tenant before returning the row. Read, write, delete: everything goes through this check. Add authentication (who the user is) and the data is isolated end to end.

Why it matters for you

If you're building a B2B SaaS, multi-tenant isolation is non-negotiable: it protects your clients and keeps you GDPR compliant. The building blocks (auth, RLS, PostgreSQL database) are already built and in production on beforbuild.com: I adapt them to your project, at a fixed price from €440 excl. tax, no subscription. Detail on Supabase developer.