EKS vs ECS vs EKS/ECS Fargate

If you are researching the various container orchestration service offerings on AWS, you may have realized that EKS and ECS are your two options. You may have also seen Fargate as an option tied to each of these service offerings, i.e. “EKS Fargate” and “ECS Fargate”, which may have further complicated your understanding of the available container orchestration service offerings on AWS.

• EKS is the managed Kubernetes service offering provided by AWS
• ECS is an AWS-specific orchestrator managed by AWS which predates EKS

While ECS is unrelated to Kubernetes, it still allows you to schedule containers and build out user-facing services out of them.

What is AWS Fargate

Fargate is a serverless execution type for each of these services which allows you to use each service without managing the underlying EC2 instances which will perform the EKS or ECS workloads.

This essentially leads to four distinct service offerings, each with its own set of constraints and nuances. The following is a simple breakdown of these nuances which may clarify your understanding of these service offerings:

Fundamental Considerations

Consideration	EKS	EKS Fargate	ECS	ECS Fargate
Container Runtime	Docker	Containerd (as of Fargate 1.4)	Docker	Containerd (as of Fargate 1.4)
Atomic Container Unit	Pod	Pod	Task	Task
Windows Container Support?	Yes, with Windows EKS Clusters	No	Yes, with Windows ECS Clusters	No

ECS and EKS Tool Ecosystem

Tool	EKS	EKS Fargate	ECS	ECS Fargate
Configuration Management	– Helm – Kustomize – Raw k8s manifests		– CloudFormation – Terraform
Centralized Logging Solution	Any centralized logging solution that can be achieved on Kubernetes (for example Fluentd running as a k8s DaemonSet as part of an EFK Stack)	– Amazon CloudWatch – Amazon Elasticsearch Service – Amazon Kinesis Data Firehose – AWS for Fluent Bit Outputs
Time Series Metrics	– Any monitoring solution that can be achieved on Kubernetes (for example Grafana and Prometheus) CloudWatch – Prometheus Metrics via CloudWatch Container Insights	Any monitoring solution that can be achieved on Kubernetes without the use of DaemonSets (for example Grafana and Prometheus, but not CloudWatch Container Insights)	CloudWatch Prometheus Metrics via CloudWatch Container Insights
Integration with ECR	Native integration with AWS ECR via IAM Policies
Integration with other Container Image Registries	Authentication with external Container Image Registries via k8s Secret objects, which are encrypted via AWS KMS

IAM and Networking

Out of Box Functionality	EKS	EKS Fargate	ECS	ECS Fargate
AWS IAM	– Cluster IAM role – Node IAM role – IAM-Role-backed Kubernetes Service Account	Pod execution role	– Amazon ECS task execution IAM role – Amazon ECS Container Instance IAM Role	Amazon ECS task execution IAM role
Networking	Amazon VPC Container Network Interface (CNI)	awsvpc — ENI allocated to each k8s Pod	– awsvpc — ENI allocated to each ECS Task – bridge — Uses EC2 instances’ Docker host networking – host — Uses EC2 instance’s ENI – none — The task has no external network connectivity	awsvpc — ENI allocated to each ECS Task

Pricing (us-east-1 as of January 2021)

Billable	EKS	EKS Fargate	ECS	ECS Fargate
Control Plane	$0.10 / hour	$0.10 / hour	None	None
CPU Time	EC2 instance pricing	$0.04048 / vCPU / hour	EC2 instance pricing	$0.04048 / vCPU / hour
Memory	EC2 instance pricing	$0.004445 / GB / hour	EC2 instance pricing	$0.004445 / GB / hour

Other Considerations

Consideration	EKS	EKS Fargate	ECS	ECS Fargate
Control Plane SLA	99.95%	99.95%	99.99%	99.99%
SLA Financially-backed?	Yes	Yes	Yes	Yes
On-prem Support (AWS Outposts)?	Yes	No	Yes	No

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