Unlimited mode for burstable performance instances

A burstable performance instance configured as unlimited can sustain high CPU utilization for any period of time whenever required. The hourly instance price automatically covers all CPU usage spikes if the average CPU utilization of the instance is at or below the baseline over a rolling 24-hour period or the instance lifetime, whichever is shorter.

For the vast majority of general-purpose workloads, instances configured as unlimited provide ample performance without any additional charges. If the instance runs at higher CPU utilization for a prolonged period, it can do so for a flat additional rate per vCPU-hour. For information about pricing, see Amazon EC2 pricing and T2/T3/T4 Unlimited Mode Pricing.

If you use a t2.micro or t3.micro instance under the AWS Free Tier offer and use it in unlimited mode, charges might apply if your average utilization over a rolling 24-hour period exceeds the baseline utilization of the instance.

T4g, T3a and T3 instances launch as unlimited by default (unless you change the default). If the average CPU usage over a 24-hour period exceeds the baseline, you incur charges for surplus credits. If you launch Spot Instances as unlimited and plan to use them immediately and for a short duration, with no idle time for accruing CPU credits, you incur charges for surplus credits. We recommend that you launch your Spot Instances in standard mode to avoid paying higher costs. For more information, see Surplus credits can incur charges and Launch burstable performance instances.