A system and method for performing incremental initialization of a master runtime system process is presented. A set of one or more warmup actions is defined from a source definition provided as object-oriented program code. A master runtime system process is executed. Each warmup action is executed to refine a memory space of the master runtime system process. The memory space is cloned as a child runtime system process responsive to a process request and the child runtime system process is executed. Initialization is incremental, such that the warmup actions are interleaved with potential requests for cloning child runtime system processes. The interleaving allows a user to interact with the master runtime system process before the full set of warmup actions are completed by the master runtime system process.