The Anatomy of a Modern SaaS Platform
The Monolith vs. Microservices
Building a Software-as-a-Service (SaaS) platform is fundamentally different from building a standard web application. A SaaS platform must handle multiple distinct organizations (tenants) simultaneously, securely isolating their data while sharing the underlying compute infrastructure to maximize profitability.
While microservices are popular, we often architect modern SaaS backends using a "Majestic Monolith" initially, separating domains logically rather than physically. This reduces networking latency and CI/CD complexity in the early growth phases, scaling into microservices only when domain boundaries strictly demand isolated compute resources.
Multi-Tenant Data Strategies
The most critical decision in SaaS engineering is data isolation. There are three primary models:
- Database-per-Tenant: Utmost security and simple backup/restore, but incredibly expensive and difficult to scale schema changes across thousands of databases.
- Schema-per-Tenant: A middle ground utilized in Postgres, offering logical separation within the same physical DB cluster.
- Shared Database, Shared Schema: The most cost-efficient and scalable method, requiring flawless Row-Level Security (RLS) to ensure tenants never see cross-pollinated data.
We deploy robust Shared Database models wrapped in strict API-gateway-level tenant validations, utilizing cutting-edge ORMs like Prisma or Drizzle to enforce tenant IDs programmatically.