Elasticity refers to the automatic scaling of resources based on demand. The benefit is that you
provision only the necessary resources at a given time (optimizing cost) and don’t have to worry
about absorbing spikes in demand.
Elasticity does not reduce interdependencies between systems – this is known as loose coupling.
Reserving capacity to reduce cost refers to using reservations such as EC2 Reserved Instances.
Selecting the correct storage tier would be an example of right-sizing not elasticity.