Build2 publishers3 min readPublished
A t3.large held at 100% CPU pays more in credit overage than for the instance itself
T8i arrives with up to 70% more compute than T3 and, by one AWS Builders account, a 20% higher hourly rate. Whether that pays back depends on how much Unlimited-mode credit overage the T3 is already accruing.
The Engineer · Build desk
What happened
- AWS made T8i generally available in four sizes only, nano through medium, each with two vCPUs presented as a single core, on custom sixth-generation Intel Xeon Granite Rapids processors and the Nitro system.
- Against T3, AWS claims up to 30% better price performance, up to 70% higher compute performance, up to 1.25x network bandwidth and up to 2.4x EBS bandwidth.
- T8i can be bought On-Demand or as Spot with a Savings Plan option listed as coming soon, supports shared tenancy only, and launched in 16 Regions across the US, Europe, Asia Pacific and Canada.
- A post in the AWS Builders channel on dev.to reports that T8i costs 20% more than T3, a figure the launch announcement does not mention.
Compiled by The EngineerSomething wrong?How this is made
Why it matters
- decision For each T3 instance the deciding input is its own Unlimited-mode overage line, and only the account holder can see that line.
- cost Anyone holding committed T3 spend is comparing a discounted rate against an On-Demand T8i rate, so the like-for-like comparison does not exist until Savings Plan coverage lands.
- constraint Because the family stops at medium, upgrading t3.large and above means leaving the burstable credit model. That is a capacity-planning exercise.
In Standard mode, a T3 that runs out of credits is clamped back to baseline, which on a t3.large is 30% per vCPU, according to the AWS Builders post on dev.to [18]. Unlimited mode bills instead of clamping: if the 24-hour average sits above baseline, AWS adds $0.05 per vCPU-hour [19]. Unlimited is the default on T8i as well [5], so overage accrues from launch.
The same post works an example. A t3.large has two vCPUs, so an instance held at 100% CPU around the clock accrues $0.10 an hour in surcharge, taking the effective rate from about $0.0835 to about $0.1835 [20]. The surcharge alone is larger than the base rate [30], and the effective price is about 2.2 times the sticker [21].
Set the reported 20% premium against that. Twenty percent of $0.0835 is about $0.017 an hour, roughly a sixth of the $0.10 surcharge [22]. The dev.to author makes the point directly: on a T3 burning credits in Unlimited mode, the faster CPU lowers credit consumption, and that saving can absorb the 20% [25]. One limit on the example is that there is no t8i.large, so a t3.large has no same-size replacement in the new family [4].
Both AWS figures are "up to". A 70% compute gain that nets out to 30% better price-performance needs an hourly rate 1.70/1.30 higher, or about 31% [23]. For that to be the real premium, both "up to" numbers would have to come from the same workload at the same instance size. The implied 31% sits above the 20% the dev.to post reports [15].
For anything bigger, AWS's own recommendation leaves the T family. Channy wrote in the launch post that workloads needing instance sizes larger than T8i's nano, micro, small and medium should go to M8i Flex, which offers up to 30% better price performance than equivalent previous generation T3 instances along with the flexibility to scale up to 16xlarge [12].
The dev.to post sorts the rest by usage pattern. Sustained-CPU workloads go to dedicated families such as c6a, m6a or c7i-flex, where credit ceilings stop producing either overage or bottlenecks [31]. A move to the c family changes the ratio to 2 GB of RAM per vCPU, and the post rates that valid only where the current T3 uses less than half its memory [26]. Keeping the ratio on m6a is rated worthwhile only where the T3 is already paying Unlimited overage [27]. For a t3.xlarge that needs its memory but not its cores, it suggests r8i-flex.large: half the vCPU count on a CPU it describes as 70% stronger than T3's, with CPU monitored after the change to confirm the result is acceptable [29].
t8i.micro and t8i.small are in the AWS Free Tier [9]. A test box is a cheap place to measure the 70% claim against your own binary. For per-Region availability and upcoming expansion, AWS points to the CloudFormation resources tab of AWS Capabilities by Region [13].
What to watch
- Whether Savings Plan coverage for T8i arrives before your current T3 commitment term ends.
- Whether AWS adds a T8i size above medium or keeps routing larger burstable workloads to M8i Flex.
- Whether the launch Region list grows enough for multi-Region fleets to standardise on T8i.