Enterprise SaaS Architecture Guide
Executive summary: Enterprise SaaS architecture is defined by three decisions made early and rarely reversed cheaply: tenancy model, data isolation strategy, and how compliance is built into the system rather than added later.
Key takeaways
- Tenancy model (pooled multi-tenant vs. isolated) is the hardest decision to reverse — get it right before writing production code.
- Compliance (SOC 2, HIPAA, PIPEDA) should shape the architecture from the start, not get retrofitted after a customer's security review flags a gap.
- Observability and infrastructure-as-code reduce long-term operating cost more than any single feature decision.
Tenancy Models, Compared
| Model | Isolation | Best fit |
|---|---|---|
| Pooled multi-tenant (row-level security) | Logical, shared infrastructure | Most SaaS products, cost-efficient at scale |
| Schema-per-tenant | Stronger logical isolation | Mid-size enterprise customers needing more separation |
| Dedicated infrastructure per tenant | Full physical isolation | Highly regulated or largest enterprise accounts |
Common Questions
What is the hardest architecture decision to reverse?
The tenancy model — changing it after launch usually requires a substantial data migration.
Do we need SOC 2 compliance from day one?
Not necessarily, but the architecture should account for it early since retrofitting is far more expensive than designing for it upfront.
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