Well my last job was working on simulations and I've only worked on performance sensitive system.... Making everything immutable maybe is silly, but it's still

Well my last job was working on simulations and I've only worked on performance sensitive system.... Making everything immutable maybe is silly, but it's still a very good goal to have in mind. A continuously evolving system can be designed in an mostly immutable manner as well without sacrificing performance. In a big picture sense you are trying to have your system be a function of time. And while for efficiency you sometimes should preserve intermediate states, you can typically accomplish that with clever caching systems that are not exposed in the interface. So the design remains "immutable" in a sense