Which Amazon Elastic Compute Cloud (EC2) pricing model should you choose for applications with short-term, spiky, or unpredictable workloads that cannot be interrupted?

Choosing On-Demand Instances for applications with short-term, spiky, or unpredictable workloads that require high availability aligns perfectly with their pricing model and use case characteristics. On-Demand Instances allow you to pay for computing capacity by the hour or second, depending on the instance type, without having to commit to a long-term contract. This flexibility ensures that your applications can scale up during peak times and reduce usage when demand decreases, making it ideal for workloads that have unpredictable usage patterns.

Moreover, On-Demand Instances guarantee that your resources are always available when needed, addressing the crucial requirement that these workloads should not be interrupted. In scenarios where uptime and immediate availability are critical, choosing On-Demand pricing offers peace of mind and reliability.

In contrast, other pricing models, such as Spot Instances, are designed for applications that can tolerate interruptions and are ideal for cost savings when the demand for instances is low. Reserved Instances require a commitment for a set term, making them less suitable for unpredictable workloads. Dedicated Instances, while providing isolated hardware for compliance or regulatory requirements, do not inherently accommodate fluctuations in demand like On-Demand Instances do. Thus, On-Demand Instances serve as the best choice for the specified workload characteristics.