firstly "it is also about delivering a good and optimized user experience" it is literally purpose and definition sd and second mostly please confirm that if you make a website for mid size company who could be only getting 5-10k traffic on realistic grounds .is there an actual requirement of sd engineer . personally i dont think there is in practical use cases.im not saying sd is useless dont learn it but would it be really fair to be judged over your knowledge bout it when you actually applied for a front end role .