Forgive me if this is answered in the book (my copy hasn't arrived yet, but I've been pouring over the source code). It seems to me that storing usernames as the keys to user records (as opposed to say an int) is highly inefficient. Sure, in ASP.NET membership, the username is fixed, but doesn't this add a lot of unnecessary data to every single forum post? For a highly active forum (say 50,000 posts), you'd be storing nearly 10MB of username data alone in the database.

I'm curious what tradeoffs went into making this decision.

Love the site and what I've seen so far of the book online, by the way. I can't wait until my copy arrives!

I think I have an answer. The datakey "Username" is chosen usually for an ASP server control, like Gridview, not as a database key. The Username is unique so can be used effectively in server controls.

I'm not sure I understand your answer... What do you mean by "chosen for server controls?" You can do a join in your select to pull the username from the ID-to-name cache table and store a bunch less data in your forums tables.

Sometimes the tables aren't in 3rd normal form because of performance concerns. I can't comment on this specific example, but the first edition suffered from some performance issues because of excessive joins needed to get data in critical paths.

Eric