A/B Testing CPU Requirement Calculator FAQ
Answers to common questions about estimating CPU cores for A/B tests, including traffic inputs, peak demand, utilization, variants, and accuracy.
Use these questions and answers to understand the inputs, results, assumptions, and limits of an A/B testing CPU capacity estimate. The calculator is intended for preliminary planning and should be checked with representative testing and monitoring.
General calculator questions
Core questions about what the calculator estimates and when to use it.
What does an A/B Testing CPU Requirement Calculator estimate?
It estimates application-serving CPU cores for the portion of traffic assigned to an experiment, using request volume, peak demand, CPU work, utilization, and headroom.
Is this result for the whole application or only the experiment?
It is for traffic included in the test. Capacity for traffic outside the experiment should be assessed separately or included by setting test traffic to 100%.
Does an A/B test inherently require double the CPU?
No. Dividing the same total traffic between control and treatment does not by itself double total request-serving CPU demand.
When should I use this calculator?
Use it for an early capacity estimate before an experiment launch, infrastructure change, or load test.
Traffic and workload inputs
How to choose the inputs that determine the request workload.
What counts as a request per user per day?
Use the relevant application or API requests that perform the workload being sized. Avoid including unrelated requests that do not use the same serving path.
How should I choose the traffic included in test percentage?
Enter the share of total relevant traffic assigned to the experiment. This is the combined experiment share across all included variants.
What is a peak traffic multiplier?
It is peak requests divided by average requests. For example, a peak rate three times the daily average uses a multiplier of 3.
Should retries be included in request volume?
Include them if they are expected during the period being planned, because retries can add application CPU work.
What CPU time per request should I enter?
Use CPU milliseconds from representative monitoring or load tests. Prefer CPU processing time rather than end-to-end latency.
Results, utilization, and variants
How to interpret the capacity outputs and allocation assumptions.
What is raw peak CPU demand?
It is the estimated core demand at 100% CPU utilization before the chosen utilization target and headroom are applied.
Why does a lower target CPU utilization increase recommended cores?
The same workload must fit within a smaller planned share of each provisioned core, so more capacity is needed.
What does additional capacity headroom cover?
It is an allowance for uncertainty, short spikes, deployment overlap, background activity, and other workload variation not fully represented by the base inputs.
How is CPU capacity per variant calculated?
The total recommended cores are divided by the number of variants, rounded up, with a minimum estimate of one core per separately allocated variant.
Can variants receive unequal traffic?
Yes. In that case, the even-split per-variant result is only a rough reference. Size each variant using its expected traffic share and CPU cost.
Accuracy and operational limits
Important constraints to consider before relying on a capacity estimate.
Does the calculator include database capacity?
No. It focuses on application CPU for request processing. Databases, caches, queues, storage, and network capacity need separate assessment.
Does the calculator account for autoscaling?
Not directly. Autoscaling speed, minimum replicas, scale-up limits, and CPU throttling can affect whether capacity is available when demand arrives.
Why might actual CPU use be higher than the estimate?
Cache misses, slow dependencies, retries, logging, telemetry, feature evaluation, background jobs, and traffic bursts can add work beyond the inputs.
Is the calculator result a production guarantee?
No. It is an estimate based on the supplied assumptions. Validate it with production-like load tests and monitor the experiment after launch.
Using the result for planning
Practical ways to use the estimate without treating it as a complete infrastructure plan.
Should I size the control and treatment separately?
Do so when they have separate deployments, unequal traffic, or different CPU cost. Compare each allocation with the total capacity requirement.
What if the calculator recommends fewer cores than my platform minimum?
Use the platform or deployment minimum as the practical allocation, then confirm it can handle the expected peak workload.
Can I calculate a 100% rollout with this tool?
Yes. Set traffic included in test to 100% to estimate the modeled request path at full relevant traffic.
What should I monitor during the experiment?
Useful signals generally include CPU utilization, throttling, request rate, error rate, latency, saturation, cache behavior, and dependency performance.
How are CPU cores calculated for an A/B test?
Peak experiment requests per second are multiplied by CPU milliseconds per request, then adjusted for the planned CPU utilization and capacity headroom.
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