Definition
A Spot instance is a form of cloud computing where users bid on unused compute capacity offered by cloud providers at significantly reduced prices. These instances are available on a flexible basis, meaning the cloud provider can reclaim them with little notice if they need the capacity back for on-demand users. This cost-effectiveness makes them ideal for fault-tolerant, flexible, or time-insensitive workloads. For example, running batch processing jobs or performing large-scale data analysis that can be interrupted and resumed is a perfect use case for Spot instances. Unlike On-Demand instances which guarantee availability, Spot instances carry the risk of interruption. Understanding Spot instances is crucial for cloud cost optimization and appears on AWS certification exams like the Solutions Architect Associate.