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Auto scaling is one of the key features of PaaS systems such as Heroku or Render. If your application isn’t used so often the auto scaling reduces the amount of required resources and thus reduces the costs. Each service starts with the minimum technical amount of resources: vCPU, RAM and Disk. If the usage exceeds a set threshold, more v CPU, RAM or Disk is allocated to the service. This is called vertical scaling. Vertical scaling is called horizontal scaling and horizontal scaling.