According to examples, a method for upgrading a version of a service may include instructing a host device to pre-spawn a number of first host processes configured to provide a first version of the service in a computing node and to pre-spawn a number of second host processes configured to provide a second version of the service according to a first scaling constraint in the computing node. The method may also include, in response to receiving an indication that each of the second host processes is operating properly, instructing the host device to decrease the number of first host processes and to increase the number of second host processes as defined in a second scaling constraint.