Horizontal Scaling

Kind: technique

Layer: Performance Core

Record: architecture:horizontal-scaling

Severity: contextual

Scope: service, infrastructure

Canonical: Ontology

A technique for adding capacity by running more stateless instances of a service behind a load balancer.

Listed in Architecture principles, after Scalability and before Vertical Scaling.

Requires

• Statelessness or Shared State Strategy

Reinforces

• Elasticity
• Availability

Enables

• Scale-Out

Conflicts with

• Instance-Local State

In tension with

• Distributed Coordination

Tensions

• Horizontal Scaling / Distributed Coordination

Violated by

• Instance Affinity

Refactored by

• Externalize Session State
• Load Balancing

Severity

• contextual

Category

• Scalability / Performance / Optimization

Reinforced by

• Competing Consumers
• Sharding
• Statelessness
• Read Replica
• Space-Based Architecture

Refactors

• Scalability
• Vertical Scaling
• Throughput
• Resource Utilization

Linked from

• A concern is a component
• Event / Messaging / Asynchronous Architecture
• Scalability / Performance / Optimization
• Codebase / System Architecture Styles
• Quality Attributes
• Scalability / Performance / Optimization
• Severity levels
• The resolutions