Becoming a SME in, let’s say Typescript (or for any statically typed language), for example easily takes 2-3 years unless you really excelled in type theory in

Becoming a SME in, let’s say Typescript (or for any statically typed language), for example easily takes 2-3 years unless you really excelled in type theory in college. Knowing the ins and outs of advanced types, generics, conditionals, etc and also having implemented these things to a degree where you can do it in your sleep. No way a junior would be able to do that. Seniors have deep knowledge of the systems/technologies that they work in and are able to articulate that to more senior management on why using that particular thing is the way to go. Obviously you want seniors to have more than just one (for both their sake and the organization) but it’s a mark that they’ve attained at least one technology that they’ve “leveled up” so to speak.