---
type: claim
domain: mechanisms
secondary_domains: [internet-finance]
confidence: proven
title: Variance pooling in large-scale systems
description: Variance pooling reduces excess capacity needs in large-scale systems by aggregating demand variability.
created: 2023-10-01
processed_date: 2023-10-10
source: 2019-00-00-whitt-what-you-should-know-about-queueing-models
---

Variance pooling is a technique used in large-scale systems to reduce the need for excess capacity by aggregating demand variability across multiple servers. At 100× scale, the pooled system requires 10× less buffer capacity than 100 separate small systems.

### Challenges
- Assumes independent and identically distributed demand.
- May not apply to systems with correlated demand patterns.

### Evidence
- Demonstrated through mathematical proofs and simulations.

### Cross-references
- Related to square-root staffing and QED regimes.