# Performance Tuning

- Canonical URL: https://docs.fairvisor.com/docs/deployment/performance-tuning/
- Section: docs
- Last updated: n/a
> Latency and capacity tuning for Fairvisor Edge.


## Goals

- Keep decision path latency low and predictable
- Avoid shared-dict pressure and hot-key contention

## Key levers

### 1) Shared dict sizing

`FAIRVISOR_SHARED_DICT_SIZE` controls in-memory limiter state capacity.

- Start at `128m`
- Increase to `256m`/`512m` for high cardinality keys
- Monitor for eviction-like behavior and unexpected limiter resets

### 2) Descriptor cardinality

Avoid unbounded key dimensions in `limit_keys`.

- Prefer stable IDs (`jwt:org_id`, `header:x-api-key`)
- Avoid raw per-request unique values as keys

### 3) Gateway timeout budget

Keep gateway->edge auth timeout tight (typical 200-500ms budget) and observe p99.

### 4) Worker and runtime tuning

- `FAIRVISOR_WORKER_PROCESSES=auto` usually works well
- Increase only after measuring CPU saturation and queueing

## Practical baseline

- `FAIRVISOR_SHARED_DICT_SIZE=128m`
- deterministic retry jitter enabled by default
- short gateway timeout and clear fail-open/fail-closed policy

## Validate after changes

- Reject/allow mix remains stable
- No spike in decision latency metrics
- No abnormal descriptor-missing metrics