Burstable Instance

A burstable instance is a virtual machine sold with a low baseline CPU level but the ability to burst above it when capacity is available. The two common accounting models are CPU credits (idle time earns credits, busy time spends them) and sustained-use baselines (a percentage of a full core, measurable at any moment).

Burstable types are significantly cheaper than fixed-performance instances of the same size and suit development boxes, small websites, and queues with idle periods. They are a poor fit for steady workloads: once credits run out, performance drops to the baseline exactly when the workload is busiest.

Before choosing a burstable type, measure your actual p95 CPU utilization. Sustained usage above the baseline means you are paying for a smaller machine at burst prices and getting throttled for it — a dedicated fixed-performance instance is usually cheaper and faster at that point.