Containerization And Microservices Modernization — AWS Solutions Architect Pro (SAP-C02)
Existing Kubernetes Investment Points to EKS, Not ECS
A company migrating from an on-premises Kubernetes cluster arrives with Helm charts, Kubernetes operators, and team knowledge built around the Kubernetes API. Rewriting those artifacts to run on ECS is a separate migration project layered on top of the cloud migration. EKS preserves that existing investment and runs the same workloads with minimal manifest changes. For greenfield container workloads with no existing Kubernetes artifacts, ECS offers lower operational overhead, native integrations with IAM, ALB, and CloudWatch, and no requirement for Kubernetes expertise. The question is not which orchestrator is architecturally superior but whether an existing Kubernetes investment would be abandoned or preserved by the choice.
What This Pattern Tests
The exam presents a monolithic application and tests decomposition strategy. The strangler fig pattern routes specific URL paths to new microservices while the monolith handles the rest — incremental, low-risk. Service boundaries follow domain boundaries (orders, inventory, payments), not technical layers. Each service owns its data store (no shared databases). Inter-service communication uses async messaging (SQS, Service Bus) for loose coupling or synchronous APIs for real-time needs. The trap is decomposing by technical layer (one "database service," one "API service") instead of by business domain.
Decision Axis
Decomposition by business domain boundaries vs. technical layers, and incremental extraction vs. full rewrite.
Associated Traps
More Top Traps on This Exam
Decision Rules
Whether ECS on Fargate or an EKS variant better satisfies a scenario where the team lacks Kubernetes expertise and the dominant constraints are eliminating patching overhead and minimizing orchestration cost — ECS on Fargate wins because it carries no control-plane fee and zero node OS lifecycle obligations, while every EKS option incurs the $0.10/hr control-plane charge and/or Kubernetes operational complexity the scenario explicitly rules out.
Domain Coverage
Difficulty Breakdown