Building a SaaS application requires careful architectural decisions. This guide covers patterns for multi-tenant systems that scale.
Multi-Tenancy Approaches
1. Database per Tenant
Each tenant gets their own database - highest isolation but most expensive.
2. Schema per Tenant
Shared database, separate schemas - good isolation with shared resources.
3. Shared Database, Shared Schema
All tenants in one table with tenant_id - most cost-effective, requires careful query building.
Key Components
API Gateway
- Rate limiting per tenant
- Authentication/Authorization
- Request routing
- Request/response transformation
Service Layer
- Business logic isolation
- Independent scaling
- Technology flexibility
Data Layer
- Connection pooling
- Tenant context in queries
- Backup strategies per tenant
Scaling Considerations
- **Horizontal scaling**: Add more instances
- **Database read replicas**: For read-heavy apps
- **Caching**: Redis for session and query caching
- **Async processing**: Message queues for background jobs
Conclusion
SaaS architecture requires balancing cost, isolation, and scalability. Start simple and evolve as you understand your tenants' needs.