EC2-Instance Scaling: Vertical & Horizontal

 

These four terms are all related to scaling in cloud or virtualized environments (like AWS EC2 or Kubernetes nodes), but they have different meanings depending on the direction and type of scaling:

 twtech-Quick Definitions:

Term	Type of Scaling	Description
Scale Out	Horizontal Scaling	Add more instances (e.g., more EC2s or pods) to distribute load.
Scale In	Horizontal Scaling	Remove instances when demand drops.
Scale Up	Vertical Scaling	Increase resources (CPU/RAM) of an instance (e.g., change or upgrade EC2 type from t2.medium to t2.large).
Scale Down	Vertical Scaling	Decrease resources of an instance (e.g., downgrade EC2 instance type).

  Horizontal vs. Vertical Scaling:

Scaling Direction	Scale Type	Examples	Use Case
Scale Out	Horizontal	Add EC2 instances, Kubernetes pods	Handle more traffic
Scale In	Horizontal	Remove EC2 instances or pods	Save cost during low usage
Scale Up	Vertical	Upgrade from t2.micro to t2.large	Need more memory/CPU
Scale Down	Vertical	Downgrade from m5.large to t3.medium	Over-provisioned system

 twtech Tips for Remembering: 

   "Out and In"          =   number of instances.

   "Up and Down"    =   power/capacity of a single instance.