saas-multi-tenant

SaaS Multi-Tenant Architecture

When to Use This Skill

• The user is building a SaaS application where multiple customers share the same database
• The user asks about tenant isolation, row-level security, or data leakage prevention
• The user needs to scope every database query to a specific tenant without manual WHERE clauses
• The user asks about shared-schema vs schema-per-tenant vs database-per-tenant tradeoffs
• The user is implementing admin endpoints that must access data across tenants
• The user needs to add tenant_id columns to an existing single-tenant application
• The user asks about PostgreSQL RLS policies for tenant isolation
• The user is building tenant-aware middleware in Express, Fastify, or Next.js API routes

Do NOT use this skill when:

• The user is building a single-user application with no shared infrastructure
• The user asks about authentication only without tenant scoping (use an auth skill instead)
• The user needs general database schema design without multi-tenancy requirements

Core Workflow

1. Determine the tenancy model. Ask the user about their scale expectations and isolation requirements. For most SaaS apps under 1000 tenants, shared-schema with a tenant_id column on every table is the correct default. Schema-per-tenant adds operational overhead (migrations run N times). Database-per-tenant is only justified when tenants have