Horizontal scaling (adding several servers to the cluster) is commonly used to improve performance and provide high availability (HA). The important advantage is that it lets increase capacity on the fly and gives more freedom to grow. But at the same time, it requires the application to be carefully designed so that it is synchronized on all instances in the cloud. Jelastic tries to ease this process on maximum for admins not to waste time on reconfigurations.

https://jelastic.medium.com/stateful-and-stateless-horizontal-scaling-for-cloud-environments-9545a8143c62