This article examines modernizing SaaS architectures by transitioning from account-per-tenant to Amazon EKS-based multi-tenant models for improved cost efficiency and resource utilization.

• Account-per-tenant model uses dedicated AWS accounts; EKS model uses shared clusters with tenant-specific namespaces
• EKS approach enables better resource utilization through dynamic scaling and shared infrastructure
• Partition customers across multiple clusters to limit blast radius and failure impact
• Containers share Linux kernel; evaluate security risks when tenants run untrusted code
• Hard multi-tenancy requires unique cluster per tenant; use Fargate for enhanced isolation
• Amazon EFS simplifies static content storage but complicates per-tenant usage metering
• Multi-tenant RDS databases lack granular per-tenant observability; use schema/user mapping workarounds
• Design tenancy strategy early; validate with prototyping before production deployment

SaaS providers should carefully evaluate security, isolation, and observability requirements when choosing between siloed and pooled multi-tenant architectures on AWS.