The general purpose T instance types are a good starting point. But depending on the CPU utilization of your workload, a fixed-CPU instance from the M or C series offers better performance for a lower price.
General
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Tinstances have a Baseline utilization per vCPU Show archive.org snapshot . - If the CPU utilization is higher than the baseline, CPU credits will be burned.
- CPU credits recharge based on instance type and CPU utilization below the baseline.
- Based on the credit specification, this happens when the EC2 instances runs out of CPU credits:
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Unlimited mode: Surplus credits will be provided and charged ( $0.05 per vCPU-Hour Show archive.org snapshot ) but performance stays the same. -
Standard mode: Performance will be capped to baseline. Notice a high CPU steal.
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- Every burstable instance has a CPU utilization break-even when a fixed-CPU instance becomes cheaper.
- The fixed CPU instances are not only cheaper at that point, they also offer better performance (e.g. through stronger CPUs).
EC2 CPU usage break-even
The AWS documentation offers a When to use unlimited mode versus fixed CPU Show archive.org snapshot calculation.
These are the break-even CPU utilizations for us-east-1:
| Burstable | Baseline utilization | Fixed-CPU | vCPU | Memory (GiB) | Break-even CPU utilization |
|---|---|---|---|---|---|
t3.medium |
20% | c7i-flex.large |
2 | 4 | 63,20% |
t3.large |
30% | m6i.large |
2 | 8 | 42,80% |
t3.xlarge |
40% | m7i-flex.xlarge |
4 | 16 | 52,55% |
t3a.medium |
20% | c6a.large |
2 | 4 | 58,90% |
t3a.large |
30% | m6a.large |
2 | 8 | 41,20% |
t3a.xlarge |
40% | m6a.xlarge |
4 | 16 | 51,20% |
