Which option should users who have urgent computing needs for large amounts of additional capacity use for optimizing costs?

Spot Instances are a cost-effective option for users who require large amounts of additional capacity urgently. They allow users to access spare Amazon EC2 capacity at significantly reduced prices compared to On-Demand instances. Spot Instances work by bidding for unused capacity, meaning that when the demand for those resources grows or exceeds your bid, your instances may be interrupted, but they typically carry a much lower cost.

This makes Spot Instances particularly suitable for various workloads, such as batch processing, big data analysis, or workloads with flexible start and end times, where cost savings can be prioritized over continuous availability. By leveraging Spot Instances, users can dynamically scale their applications and handle spikes in demand without incurring the significant costs associated with traditional On-Demand pricing.

On the other hand, On-Demand Instances provide flexibility but at a premium price, making them less ideal for users looking for cost optimization. Reserved Instances offer cost savings for long-term workloads in exchange for a commitment to using a specific instance type for a one or three-year term, which may not address urgent, fluctuating capacity needs rapidly. Dedicated Hosts are designed for scenarios where users need to use physical servers for compliance or licensing requirements, generally resulting in higher costs without the cost-saving benefits of Spot Instances.