# Capacity Planning

- Canonical URL: https://docs.fairvisor.com/docs/reference/capacity-planning/
- Section: docs
- Last updated: n/a
> Estimate memory/cardinality requirements for limiter state.


## Input dimensions

- active unique limit keys per window
- algorithms used (`token_bucket`, `cost_based`, `token_bucket_llm`)
- expected concurrency and burst profile
- retention/reset windows

## Practical sizing workflow

1. Estimate unique active keys per critical rule
2. Start with `FAIRVISOR_SHARED_DICT_SIZE=128m`
3. Load test with realistic cardinality
4. Increase to `256m`/`512m` if signs of state pressure appear

## Rule-of-thumb table

| Active key cardinality | Starting dict size |
|---|---|
| <= 100k | `128m` |
| 100k-250k | `256m` |
| 250k-500k | `512m` |
| > 500k | profile and shard strategy |

## Validate after sizing

- stable allow/reject semantics under load
- no abnormal limiter resets
- latency remains within SLO at p95/p99