Multi-Tenancy Patterns for Modern SaaS Applications

Designing Isolated SaaS Architectures

When building a Software-as-a-Service platform, selecting the correct multi-tenancy model is one of the most critical structural decisions you will make. It impacts security compliance, database performance, backup strategies, and infrastructure costs.

The Three Principal Approaches

There are three main patterns for segregating customer data, each with distinct benefits and architectural trade-offs:

• Database-per-Tenant: Complete logical separation. Easiest for custom compliance and custom backups, but highly expensive to maintain and scale.
• Schema-per-Tenant: Multiple isolated schemas within a single shared database. A solid middle ground for PostgreSQL systems.
• Shared Database, Row-Level Isolation: High density and low cost. Tenant segregation is enforced via code queries or database Row-Level Security (RLS) policies.

Implementing Row-Level Security in PostgreSQL

For high-scale, cost-effective SaaS products, we recommend Postgres RLS. It locks down queries at the database layer, protecting against developer slip-ups that might expose other tenants' data.

-- Enable RLS on the users table
ALTER TABLE users ENABLE ROW LEVEL SECURITY;

-- Create policy to restrict queries to tenant ID
CREATE POLICY tenant_isolation_policy ON users
  USING (tenant_id = current_setting('app.current_tenant_id'));