# Suboptimal use of on-demand instances in fault-tolerant EC2 workloads Canonical: https://www.pointfive.co/efficiency-hub/inefficiencies/suboptimal-use-of-on-demand-instances-in-fault-tolerant-ec2-workloads Many EC2 workloads - such as development environments, test jobs, stateless services, and data processing pipelines-can tolerate interruptions and do... By: Matt Weingarten Updated: 2026-09-28 [Cloud Efficiency Hub](https://www.pointfive.co/efficiency-hub) # Suboptimal Use of On-Demand Instances in Fault-Tolerant EC2 Workloads The short version Many EC2 workloads - such as development environments, test jobs, stateless services, and data processing pipelines-can tolerate interruptions and do not require the reliability of On-Demand pricing. Matt Weingarten AWS service [AWS EC2](https://www.pointfive.co/efficiency-hub/cloud-services/aws-ec2) Category [Compute](https://www.pointfive.co/efficiency-hub/service-category/compute) Reference CER-0012 Type Suboptimal Pricing Model ## Explanation Why the waste happens and who it affects. Using On-Demand instances in these scenarios drives up cost without adding value. Spot Instances offer significantly lower pricing and are well-suited to workloads that can handle restarts, retries, or fluctuations in capacity. Without evaluating workload tolerance and adjusting pricing models accordingly, organizations risk consistently overpaying for compute. ## Billing model The pricing dimensions that drive this cost. EC2 is billed based on: - Instance Type and Size - determines the base hourly rate - Pricing Model - On-Demand: Highest cost, flexible usage - Spot: Deep discounts with interruption risk - Reservations/Savings Plans: Lower cost for committed usage On-Demand usage incurs the highest hourly rate. When applied to fault-tolerant workloads, it often leads to avoidable overspending. ## How to detect 4 checks to find it in your estate. - Identify EC2 instances in non-production environments or batch frameworks running on On-Demand - Review Auto Scaling Group and launch template settings for pricing model selection - Cross-check usage patterns against workload type and fault tolerance characteristics - Engage engineering teams to validate whether On-Demand usage is justified ## How to fix 4 ways to remove the waste. - Reconfigure eligible workloads to use Spot Instances via launch templates or Auto Scaling policies - Use mixed-instance groups with the price-capacity-optimized allocation strategy, diversified across many instance types and Availability Zones - Apply On-Demand only where availability, SLA, or licensing requirements demand it - Encourage team-level cost reviews to identify low-risk transitions to Spot ## Documentation Vendor references for pricing and configuration. - [AWS Spot Instances docs.aws.amazon.com](https://docs.aws.amazon.com/AWSEC2/latest/UserGuide/using-spot-instances.html) - [EC2 Pricing Models Overview aws.amazon.com](https://aws.amazon.com/ec2/pricing/) ## Related inefficiencies [Browse the library](https://www.pointfive.co/efficiency-hub) - AWS EC2 CER-0324 ### [Excessive On-Demand Compute Spend Due to Low Savings Plan and Reserved Instance Coverage](https://www.pointfive.co/efficiency-hub/inefficiencies/excessive-on-demand-compute-spend-due-to-low-savings-plan-and-reserved-instance-coverage) AWS compute services charge the full published On-Demand rate when no commitment-based discount - such as a Savings Plan (SP) or Reserved Instance (RI) - is in effect. On-Demand pricing provides maximum flexibility, but it is also the most... Compute - AWS EC2 CER-0108 ### [Suboptimal Use of Compute Savings Plans for Specialized Instances](https://www.pointfive.co/efficiency-hub/inefficiencies/suboptimal-use-of-compute-savings-plans-for-specialized-instances) Accelerated EC2 instance types such as \`p5.48xlarge\` and \`p5en.48xlarge (often used for ML/AI workloads)\` are eligible for Compute Savings Plans, but the discount rates offered are modest compared to more common instance families. When... Compute - AWS EC2 CER-0327 ### [Spot Instance Overreliance Without Effective Cost-Per-Performance Analysis](https://www.pointfive.co/efficiency-hub/inefficiencies/spot-instance-overreliance-without-cost-per-performance-analysis) Organizations frequently pursue aggressive Spot Instance adoption based on headline discount percentages - up to 90% off On-Demand pricing - without evaluating the effective cost per unit of work completed. While Spot pricing can deliver... Compute --- Source: the public page above. Product screenshots and illustrative interfaces are examples, not live customer data.