Rapid elasticity is the ability of a cloud service to scale up or down the resources (such as virtual servers, storage, bandwidth, etc.) according to the demand of the users. This is an efficient way to handle unusually high web traffic usage, as it allows the company to provision more virtual servers when needed and release them when not needed, without wasting resources or paying for unused capacity. Rapid elasticity also improves the performance and availability of the web service, as it can adjust to the fluctuations in traffic and avoid overloading or downtime.