What Multi-Tenancy Means for SaaS
Multi-tenancy means one instance of your software serves multiple customers (tenants), with each customer's data isolated from others. As a SaaS founder you want multi-tenancy because you maintain one codebase and one infrastructure deployment instead of one per customer. Your customers want it because they get automatic updates and do not manage infrastructure. The architectural challenge is data isolation: tenant A must never see tenant B's data, even accidentally.
Approach 1: Shared Database, Shared Schema (Recommended for MVPs)
All tenants share the same database tables. Every table has a tenant_id column, and every query filters by tenant_id. This is the simplest approach: minimal infrastructure cost, easy to deploy and maintain, and scales to thousands of tenants on a single database. The risk: a bug that forgets to filter by tenant_id can expose cross-tenant data. Mitigate with row-level security (RLS) in PostgreSQL — the database enforces the filter even if the application code forgets. Shopify, Intercom, and most SaaS companies under $100M ARR use this approach.
Approach 2: Schema-Per-Tenant (For Compliance-Sensitive Use Cases)
Each tenant gets their own database schema (like a namespace). All tables are duplicated per schema, and the application switches schemas on each request. Better data isolation, easier per-tenant backups, and easier to migrate individual tenants. Cost: significantly more complex migrations (schema changes must run across all tenants), harder to query across tenants for analytics. Used when tenants need strong data isolation guarantees (healthcare, banking).
Approach 3: Database-Per-Tenant (For Enterprise Customers Only)
Each tenant gets their own database instance. Maximum isolation, per-tenant SLAs, easy data residency compliance. But: cost scales linearly with tenant count (each database has baseline infrastructure cost), migrations are complex, and operational overhead is significant. Only justified for enterprise customers paying ₹5 lakh+/year who contractually require it. Contact hello@devxaitechnologies.com to architect your SaaS platform.