Scalability is a characteristic of cloud computing that is used to handle the increasing workload by increasing in proportion amount of resource capacity. By the use of scalability, the architecture provides on-demand resources if the traffic is raising the requirement.
Whereas, Elasticity is a characteristic that provides the concept of commissioning and decommissioning of a large amount of resource capacity dynamically. It is measured by the speed at which the resources are on-demand and the usage of the resources.