Yeah unless you are designing the replacement for a system that has already reached it's scalability limits you shouldn't be worrying too much other than not do

Yeah unless you are designing the replacement for a system that has already reached it's scalability limits you shouldn't be worrying too much other than not doing very silly things architecturally. When you are designing replacements though you need to have an idea of what your scalability runway is before the next re-design will be possible. Sometimes that is just 2x, often times it's 10x, occasionally it's 100x but it's all situational.