A batch processing job runs on EC2 instances for 90 minutes each weekend, tolerates interruptions, and will run weekly for six months. Which EC2 purchasing option is the most cost-effective for this workload?

Spot Instances are the most cost-effective option because the workload is fault-tolerant and can handle interruptions. Spot Instances leverage unused EC2 capacity, offering significant discounts (up to 90% off On-Demand prices) in exchange for the possibility of being interrupted if EC2 needs the capacity back. Given the job runs only 90 minutes each weekend for six months, the cost savings outweigh the minimal risk of interruption for this specific use case. Reserved Instances are designed for steady-state, predictable workloads running 24/7 for one or three years, offering less flexibility and higher commitment than needed here. On-Demand Instances are more expensive as they offer no discount for commitment or interruption tolerance. Dedicated Instances provide physical isolation for regulatory compliance, which is unnecessary and much more expensive for this batch processing job.