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Cloud Computing · Foundational

Horizontal Scaling

Increasing or decreasing capacity by adding or removing instances or nodes; also called scaling out/in.

Definition

Horizontal scaling distributes load across more identical resources, usually behind a load balancer, and is the basis of cloud elasticity. It improves availability and has near-unlimited ceiling, but applications must be stateless or externalize session state.

Example

An Auto Scaling group adds two EC2 instances to the target group when average CPU exceeds 60 percent.

Exam tip

Horizontal scaling is the preferred cloud pattern; storing sessions locally on instances is the classic obstacle to it.

Don't confuse it with

Related terms