Multi-Tenancy Isn’t About Databases

This article argues that multi-tenancy in SaaS applications is often mistakenly reduced to a database question (shared vs. per-tenant). It highlights the pitfalls of shared infrastructure, such as performance coupling and deployment failures from non-backward-compatible schema changes. The author emphasizes that the real goal is isolation across multiple dimensions: data, compute, deployments, schema changes, performance, and failure types. True multi-tenancy requires creating boundaries beyond just databases, using patterns like blue-green or canary deployments and considering trade-offs. The article is a technical guide for software architects and developers designing scalable, resilient multi-tenant systems.