I would like to know how Stackoverflow and StackExchange manage pre-defined tags tags and addition of new tags. Today, I tried to define a new tag, only to be met with this error message:
Creating the new tag 'mcrouter' requires at least 300 reputation. Try something from the existing tags list instead.
I am interested to know how the data model that deals with pre-defined tags and new tags, especially dealing with the 300 count. Is the counter installed in a table? How is this achieved on the data level? Or is this done on the code level?