Take for example this random question: Tool or plugin required to show out in which html files a given css selectors is used, notice that the relevant part is /questions/16999.
Now, it being possible that the url could have been done like this :
https://webmasters.stackexchange.com/questions/tool-or-plugin-required-to-show-out-in-which-html-files-a-given-css-selectors-is/16999`
That is the question_id is after the question, and what comes first in a url weighs more in seo, why is the question part coming after the question_id.
I also read in an article that only the first two subdirectories are relevant therefore only /question/16999 is relevant. Looking at SO this is definitely not true, but I can't decide on the weigh of this.
I am asking because I am going to implement seo optimizations and don't want to have to change the link to my pages afterwards.