SaaS Multi-Tenancy

SaaS Multi-tenancy Database Design

Multi-tenancy is a core SaaS architecture concern: multiple customers share infrastructure while maintaining data isolation.

Three Models

• Database per Tenant: Maximum isolation, highest cost, O(N) ops complexity
• Schema per Tenant: Good isolation, shared instance, 500 tenant limit
• Shared Tables: Lowest cost, tenant_id column on every table, noisy neighbor risk

Shared Schema Pattern

Every table gets a tenant_id column with an index. Application middleware injects tenant context from JWT/subdomain. Repositories always filter by tenant_id — never write a query without it.

Noisy Neighbor Mitigation

• Use MAX_EXECUTION_TIME hint for large queries
• Route batch exports from free-tier tenants to read replicas
• Partition by tenant_id range to reduce hot spots

Custom Fields

JSON column is simplest: custom_fields JSON. Create functional indexes on frequently-queried keys: ((custom_fields->>'$.industry')).