A system for executing software, wherein a computing device stores first software instructions for a code execution module such that, when the first software instructions are executed, the computing device will: receive, for execution by the code execution module, second software instructions; create one or more immutable software nodes described in the second software instructions; determine that the second software instructions comprise an instruction to begin a simulated change at runtime of the one or more immutable software nodes; store the simulated change in a simulated change apparatus; using the simulated change apparatus, perform one or more operations of the second software instructions as if the one or more immutable software nodes had been changed in memory, during a period of time where each of the one or more immutable software nodes is guaranteed to retain logical immutability; and output results of the one or more operations.