Multi-tenant SaaS is a software-as-a-service architecture where one application instance serves multiple isolated customer accounts (tenants), with logical or physical separation of each tenant's data.
Multi-tenancy is the foundational pattern of modern cloud software. Tenants share underlying infrastructure (compute, database, CDN) while their data and configuration remain isolated through tenant identifiers on every table and request-routing logic that scopes queries to the active tenant.
For ecommerce, "multi-tenant SaaS" describes the platform vendor's architecture (e.g., Ordiko, Shopify, BigCommerce all run multi-tenant under the hood). Sometimes the term gets confused with multi-store — multi-tenant SaaS is about how the vendor serves customers; multi-store is about how one customer operates multiple storefronts.
In a multi-tenant ecommerce platform, tenant isolation typically operates at row-level (storeId column on every product, order, customer) with middleware enforcing the active tenant via subdomain, custom domain, or path prefix.