Hi.
Unfortunately you posted only one of the queries, so one cannot weight
in their complexity.
First, normally forums get at least about 10 times more read requests
than new posts. In my experience posting speed is not a limiting
factor. That said, I am going to answer your original question.
I am building a forum as part of a site, and the forum is broken into three
tables, a forum table, a thread table, and a post table.
All tables have indexes for common SELECT statements, to increase speed.
Example-
A user posts a new thread: One method would be 3 queries to insert/update
(insert
