> you need to quickly prototype, refactor the code or make changes under a strict deadline, not good

How many projects like this shouldn't be written in C++ in the first place? C++ isn't automatically faster than Java, and with the level of care you're describing ("strict deadlines, just get it done") you're unlikely to realize the advantage of C++.

Rust is a lot better at quick prototyping than C++. There is a specific idiom to writing prototype "throwaway" code in Rust though, where you .clone() and use RefCell<> and Rc<> a lot more than you normally would (not to mention really niche features like Any). The advantage is that this boilerplate guides you when refactoring the code for better reliability and performance later on.