November 23, 2018

In Cloud Computing, What is the Difference Between Scalability and Elasticity

In Cloud Computing, we often hear the terms 'Scalability' and 'Elasticity' being thrown around, often being used interchangeably. Recently, I was listening to an online course describing Cloud Computing concepts, and the way these two terms are described got me thinking about the differences.

So far, there is no general consensus on how to draw the line. I have seen explanations which put Scalability as adding resources while Elasticity as adding AND removing resources. I have also seen descriptions that says Scalability is to be able to scale an instance's resources, while Elasticity is to be able to add/remove additional instances.

I am of the opinion that demarcating the differences purely from the perspective of resource adding and removing is too simplified and a little ambiguous, while the latter view of instance resource vs new instances is really still talking about Scalability (Vertical Scaling vs Horizontal Scaling - explained at the end of this article).