CPU credit balance suddenly dropped for my instance - AWS

Question

I am using a T2 EC2 instance and the CPU credit balance suddenly dropped for my instance. Why did this happen?

Answer 1

Hi @Hannah, when you stop your instance all your acquired credits are removed. When you relaunch an instance you have zero acquired credits and only left with launch credits. 

So basically your CPU credit balance increases if the credits spent are less than credits earned in the first 5-minute interval for starting the instance and vice versa. 

Mathematically your earned credits can be calculated using the following formula:

CPUCreditBalance = prior CPUCreditBalance + [Credits earned per hour * (5/60) - CPUCreditUsage]

For monitoring your CPU credits, have a look at this: https://docs.aws.amazon.com/AWSEC2/latest/UserGuide/burstable-performance-instances-monitoring-cpu-credits.html