A/B Testing Memory Requirement (Per-User) Calculator
Estimate the memory required per user to store A/B test assignments, tracked events, profile data, and system overhead.
Overview
This A/B testing memory requirement calculator estimates how much data is stored for each user when you retain experiment assignments, event records, profile data, and an allowance for storage overhead. It can help with early capacity planning for an experimentation system.
How it works
The calculator multiplies active experiments by retained events and the average size of each event to estimate event storage. It separately calculates assignment storage, adds base profile data, and then increases the total by your overhead percentage. Results use 1 KB = 1,024 bytes and 1 MB = 1,048,576 bytes.
How to use this calculator
- 1Enter the average number of active experiments assigned to each user.
- 2Add the average number of event records retained per experiment.
- 3Estimate the average serialized size of each event record in bytes.
- 4Enter the bytes used by each experiment assignment and the base user profile.
- 5Add an overhead allowance and review the estimated storage per user.
Example Calculation
Active experiments per user
5
Stored events per experiment
20
Average event record size
500
Experiment assignment size
100
Base user profile size
2000
Storage overhead
30%
Estimated memory per user
66.65 KB
With five experiments, 20 retained 500-byte events per experiment, 100-byte assignments, a 2,000-byte profile, and 30% overhead, the estimate is 67,600 bytes, or about 66.02 KB per user.
Frequently asked questions
What does per-user A/B testing memory mean?
It is an estimate of the storage allocated to one user’s experiment assignments, retained test events, profile data, and related overhead.
Should I include every analytics event in events per experiment?
Include the events that your experimentation system stores or retains specifically for each user and experiment. Exclude data held elsewhere if it is not part of this storage design.
Why is storage overhead needed?
Stored data usually requires additional space for indexes, record headers, serialization, database structures, and similar operational needs.
Does this calculator estimate total storage for all users?
It estimates storage for one user. Multiply the per-user byte result by your expected user count to create a rough total storage estimate.
Does compression reduce the result?
It can. Compression effectiveness depends on the data format, repeated values, database technology, and whether data is stored in rows, columns, or logs.
Is this the same as application RAM usage?
No. This calculator estimates retained data storage per user. Runtime RAM use can also depend on caching, query workloads, services, and concurrent traffic.
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Assumptions and warnings
Assumptions
- Each user is enrolled in the average number of active experiments entered.
- Each experiment retains the same average number and size of event records per user.
- The overhead percentage covers storage overhead but may not fully reflect backups, replication, or infrastructure-level capacity.
- Values are storage estimates and do not measure runtime memory used by application processes.
Warnings
- Actual database storage can differ substantially because of compression, indexing, record layout, retention policies, replication, and caching.
- Use measured production or representative test data when making capacity or infrastructure decisions.