Supabase RLS patterns for multi-tenant apps

Row Level Security (RLS) is most effective when paired with clear ownership and tenant boundaries. Define your data model with tenant/organization IDs first, then write policies that enforce access control at the database layer.

Treat every query as untrusted by default and validate access through policies. Don't rely on application-layer filtering alone. Use Postgres policies to ensure that even if your application has a bug, the database enforces correct permissions.

Keep service role keys server-only and prefer parameterized queries and validated inputs. Never expose the service role key to your frontend or client applications. Use row-level security with proper JWT claims to validate requests.

Real-world example: for a multi-tenant SaaS, create a policy that compares auth.jwt() against the organizations.id column. This ensures users can only see and modify data belonging to their organization, enforced by Postgres itself.