A team runs a t3.medium EC2 instance for a workload that is mostly idle but occasionally needs to sustain CPU usage above the instance's baseline for extended periods. With the default 'Standard' credit configuration, performance drops sharply once accumulated CPU credits run out. Which change lets the instance sustain high CPU performance during these bursts, while accepting that AWS may charge extra for the additional usage?
- Switch the instance's credit specification to Unlimited mode
- Move the instance into a Spread placement group
- Enable EBS optimization on the instance
- Change the Auto Scaling group's health check type to ELB
Correct answer: A. Switch the instance's credit specification to Unlimited mode
Burstable instances like t3.medium accumulate CPU credits while running below their baseline performance and spend them to burst above it; in Standard mode, once credits are exhausted, CPU performance is throttled back down to the baseline. Switching the credit specification to Unlimited mode lets the instance burst above baseline for as long as needed, with AWS billing any surplus usage beyond what earned credits cover, which directly solves the described problem. A Spread placement group only changes which underlying hardware instances land on for fault isolation; it has no effect on CPU credit behaviour. Enabling EBS optimization dedicates bandwidth to EBS volume traffic and improves storage throughput, but does not touch CPU credit throttling. Changing an Auto Scaling group's health check type from EC2 to ELB affects how unhealthy instances are detected and replaced, which is unrelated to a single instance's CPU performance ceiling.
Source: AWS EC2 documentation: Burstable performance instances — Unlimited mode