What is AWS ECS and EKS for containers?
Why Interviewers Ask This
Candidates at the intermediate level are expected to not only know this concept but explain the trade-offs involved. Interviewers use this question to see if you can reason about design decisions, not just recall facts.
Answer
AWS provides two managed container orchestration services: Amazon ECS (Elastic Container Service): AWS-native container orchestration. Launch types: EC2 (you manage EC2 instances in a cluster) or Fargate (serverless — no EC2 management). Key concepts: Cluster (group of capacity), Task Definition (blueprint — Docker image, CPU, memory, env vars, ports, IAM role, logging), Service (maintain N running tasks, integrate with ELB), Task (running instance of a task definition). Integration: ECR (private container registry), ALB with dynamic port mapping, CloudWatch Logs, IAM task roles (like EC2 instance profiles), Service Auto Scaling. ECS Anywhere: run ECS tasks on on-premises servers. Amazon EKS (Elastic Kubernetes Service): managed Kubernetes — AWS manages the Kubernetes control plane (API server, etcd, scheduler). Node groups: managed (AWS manages provisioning and lifecycle), self-managed, Fargate (serverless pods). Features: Kubernetes-standard — portable across clouds; AWS integrations (EBS, EFS, ALB, IAM via IRSA); Karpenter (node autoscaler — more flexible than Cluster Autoscaler); EKS Anywhere (on-premises). ECS vs EKS: ECS is simpler, tighter AWS integration, less operational overhead, AWS-proprietary. EKS is standard Kubernetes — portable, larger ecosystem, steeper learning curve, more flexible. Choose ECS for simpler AWS-native workloads; EKS for teams with Kubernetes expertise or multi-cloud portability needs. AWS Fargate: serverless compute for containers — no EC2 instances to manage. Works with both ECS and EKS. Pay per vCPU and memory per second.
Pro Tip
Back up your answer with a specific project or situation. Saying 'In my last AWS / Cloud Computing project, I used this when...' immediately makes your answer more credible and memorable.