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EKS vs ECS: Detailed Comparison

This document provides a comprehensive comparison between the AWS ECS and AWS EKS implementations in this project, helping you understand the trade-offs between these two container orchestration approaches.

Key Differences

1. Container Orchestration

ECS:

  • AWS-proprietary container orchestration
  • Task definitions define containers
  • ECS service manages desired count
  • Tightly integrated with AWS services

EKS:

  • Standard Kubernetes (K8s) orchestration
  • Deployments + Pods define containers
  • ReplicaSets manage desired count
  • Portable across clouds (AWS, GCP, Azure, on-prem)

2. Networking

ECS:

  • ECS tasks use ENIs (awsvpc mode)
  • ALB target groups register tasks directly
  • Security groups on tasks

EKS:

  • Pods use AWS VPC CNI for IP addresses
  • ALB Ingress Controller creates target groups
  • Security groups on nodes + network policies

3. Scaling

ECS:

  • ECS Capacity Provider scales EC2 instances
  • ECS Service Auto Scaling scales tasks
  • Target tracking based on CPU/memory

EKS:

  • Cluster Autoscaler scales nodes
  • Horizontal Pod Autoscaler (HPA) scales pods
  • Metrics Server provides resource metrics

4. Service Discovery

ECS:

  • AWS Cloud Map for service discovery
  • ALB for external load balancing
  • ECS service connects to target groups

EKS:

  • Kubernetes DNS (CoreDNS) for service discovery
  • AWS Load Balancer Controller for external LB
  • Ingress resources create ALBs automatically

5. IAM Permissions

ECS:

  • Task Role: IAM role for application
  • Execution Role: IAM role for ECS agent
  • Directly attached to task definition

EKS:

  • ServiceAccount: Kubernetes identity for pods
  • IRSA (IAM Roles for Service Accounts): Maps K8s SA to IAM role
  • Annotated on ServiceAccount

ECS → EKS Component Mapping

ECS Component EKS Equivalent Description
ECS Cluster EKS Cluster Control plane for container orchestration
ECS EC2 Launch Template + ASG EKS Node Group Managed EC2 instances running Kubernetes
ECS Task Definition Kubernetes Deployment Application container specifications
ECS Service Kubernetes Service + Ingress Load balancing and service discovery
ALB Target Group AWS Load Balancer Controller Ingress controller managing ALB
ECS Task Role Kubernetes ServiceAccount + IRSA Pod-level IAM permissions

Summary Comparison

Aspect ECS (infra-ecs/) EKS (infra-eks/)
Orchestration AWS ECS (proprietary) Kubernetes (open-source)
Control Plane Free, managed by AWS ECS Not free, managed by AWS EKS
Total Monthly Cost Cheap (x) Expensive (2x)
Learning Curve Easier Steeper
Complexity Lower Higher
Portability AWS-only Multi-cloud
Ecosystem AWS services Kubernetes ecosystem
Load Balancing ALB managed by Terraform ALB managed by Ingress Controller
Scaling ECS Service auto-scaling + Capacity Provider Horizontal Pod Autoscaler (HPA) + Cluster Autoscaler
Workload Definition Task Definition + Service Deployment + Service + Ingress
Networking awsvpc mode with ENI per task Kubernetes CNI (AWS VPC CNI)
Use Case AWS-committed workloads Kubernetes-native or multi-cloud

Can I Run Both Simultaneously?

Yes! The implementations use separate Terraform state files (deployment/ vs deployment/app/) and independent resources, allowing side-by-side deployment for comparison.

This allows you to:

  • Compare performance and behavior between ECS and EKS
  • Test migration strategies
  • Evaluate which approach better fits your use case
  • Learn both orchestration platforms hands-on

Related Documentation:

Last Updated: 2026-01-09