# Idle ECS container instances due to ASG minimum capacity Canonical: https://www.pointfive.co/efficiency-hub/inefficiencies/idle-ecs-container-instances-due-to-asg-minimum-capacity When ECS clusters are configured with an Auto Scaling Group that maintains a minimum number of EC2 instances (e.g., min = 1 or higher), the instances... By: Akarsh Inuganti Updated: 2026-09-28 [Cloud Efficiency Hub](https://www.pointfive.co/efficiency-hub) # Idle ECS Container Instances Due to ASG Minimum Capacity The short version When ECS clusters are configured with an Auto Scaling Group that maintains a minimum number of EC2 instances (e.g., min = 1 or higher), the instances remain active even when there are no tasks scheduled. Akarsh Inuganti AWS service [AWS ECS](https://www.pointfive.co/efficiency-hub/cloud-services/aws-ecs) Category [Compute](https://www.pointfive.co/efficiency-hub/service-category/compute) Reference CER-0139 Type Idle or Unused Resource ## Explanation Why the waste happens and who it affects. This leads to idle compute capacity and unnecessary EC2 charges.Instead, ECS Capacity Providers support target tracking scaling policies that can scale the ASG to zero when idle and automatically increase capacity when new tasks or services are scheduled. Failing to adopt this pattern results in persistent idle infrastructure and unnecessary costs in ECS environments that do not require always-on compute. ## Billing model The pricing dimensions that drive this cost. - EC2 container instances in ECS are billed like regular EC2 instances - by the second, based on type and size - ASGs that maintain a minimum capacity \> 0 will keep EC2 instances running even if no ECS services or tasks are scheduled - ECS Capacity Providers can scale ASGs dynamically using target tracking, enabling min = 0 when idle ## How to detect 4 checks to find it in your estate. - Identify ECS clusters using EC2 launch type - Check the associated ASG for a minimum capacity \> 0 - Analyze task scheduling patterns to confirm periods of inactivity - Correlate EC2 uptime with lack of ECS service or task activity ## How to fix 4 ways to remove the waste. - Configure an ECS Capacity Provider for the cluster and attach a target tracking scaling policy - Set the ASG minimum capacity to 0 to allow scale-down during idle periods - Ensure ECS services are configured with appropriate scaling triggers (e.g., CPU or memory utilization) - Monitor for unintended delays when new tasks are scheduled to validate scaling responsiveness ## Documentation Vendor references for pricing and configuration. - [Amazon ECS capacity providers for EC2 workloads docs.aws.amazon.com](https://docs.aws.amazon.com/AmazonECS/latest/developerguide/asg-capacity-providers.html) - [Automatically manage Amazon ECS capacity with cluster auto scaling docs.aws.amazon.com](https://docs.aws.amazon.com/AmazonECS/latest/developerguide/cluster-auto-scaling.html) - [Amazon ECS managed scaling behavior docs.aws.amazon.com](https://docs.aws.amazon.com/AmazonECS/latest/developerguide/managed-scaling-behavior.html) ## Related inefficiencies [Browse the library](https://www.pointfive.co/efficiency-hub) - AWS ECS CER-0341 ### [Idle ECS Service on Fargate](https://www.pointfive.co/efficiency-hub/inefficiencies/idle-ecs-service-on-fargate) An Amazon ECS service keeps its desired count of tasks running indefinitely: if a task stops, the scheduler starts a replacement. When the application behind a service is retired, replaced by a new service, broken, or simply no longer... Compute - AWS ECS CER-0340 ### [Overprovisioned ECS Task Size on Fargate](https://www.pointfive.co/efficiency-hub/inefficiencies/overprovisioned-ecs-task-size-on-fargate) Amazon ECS tasks on Fargate must declare CPU and memory at the task level, chosen from a fixed set of valid combinations, and Fargate bills for that configured size for as long as each task runs. What the containers actually consume does... Compute - AWS ECS CER-0360 ### [ECS on EC2 Without Binpack Task Placement](https://www.pointfive.co/efficiency-hub/inefficiencies/ecs-on-ec2-without-binpack-task-placement) When Amazon ECS runs tasks on EC2 container instances, the placement strategy decides which instance each task lands on. Services default to spreading tasks across Availability Zones, and many teams also spread by instance ID or use random... Compute --- Source: the public page above. Product screenshots and illustrative interfaces are examples, not live customer data.