A/B Testing Memory Requirement Per-User Calculator FAQ
Answers to common questions about estimating A/B testing per-user storage, inputs, overhead, and result interpretation.
This FAQ explains what the calculator estimates, how to choose its inputs, and why actual storage can differ from a modelled per-user result.
General Questions
Basic scope and intended use of the calculator.
What does per-user A/B testing memory mean?
It is an estimate of retained storage associated with one user's experiment assignments, experiment events, profile data, and a storage-overhead allowance.
Is this calculator for storage or application memory?
It estimates retained data storage. Application RAM can additionally depend on caching, processes, traffic, and query patterns.
Who can use this calculation?
It can support early scenario modelling for teams designing or reviewing an experimentation data system.
Inputs and Components
How the input fields contribute to the result.
What counts as an active experiment per user?
Use the average number of experiments where a user has an assignment that is retained in the storage design being estimated.
Which events should be included?
Include event records retained per user and per experiment in the system being modelled. Exclude data kept only in an unrelated system.
What belongs in an event record size?
Consider the serialized event payload, identifiers, timestamps, properties, and any per-record metadata that is stored with it.
What is base profile size?
It is the user-level data stored alongside experimentation records, such as selected attributes or profile metadata.
Formula and Units
Questions about the calculation method and output units.
How are event records calculated?
Event data equals active experiments multiplied by stored events per experiment and average bytes per event.
How are assignment records calculated?
Assignment data equals the number of active experiments multiplied by the bytes required for one assignment.
Why are results shown in KB and MB?
They make byte totals easier to read. The calculator uses 1 KB = 1,024 bytes and 1 MB = 1,048,576 bytes.
Does overhead apply only to event data?
No. The selected percentage is applied to the combined raw total of profile, event, and assignment data.
Accuracy and Capacity Planning
Important factors that can make deployed storage differ from the estimate.
Why might actual storage differ from the estimate?
Compression, indexes, data layout, retention policy, replication, and implementation details can all change actual storage use.
Should replication be entered as storage overhead?
You may model some related allowance in overhead, but replica and backup requirements are often clearer as separate capacity scenarios.
Does compression reduce the calculated result?
It may, but the effect depends on data content, encoding, storage technology, and access patterns. Use measured data when available.
How can I improve the estimate?
Measure representative stored record sizes and model low, typical, and high-retention scenarios.
How is A/B testing memory per user calculated?
The calculator adds profile data, retained event data, and assignment data, then applies the chosen storage-overhead percentage.
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