What are we using: Windows 2008 R2. Moodle 2.3 MySQL Innodb.
Each quiz question is its own page. When the student clicks next to go to the next question there is a delay while the next question loads.
I have tuned teh database some. It helped speed the entire site up and reduced the quiz question dely by about .66 seconds. But there is still a delay.
I have reviewed all the other suggestions for performance and they don't apply--filters, language packs, reports, etc.
I turned slow querying on (this is MySQL) and the quiz does put some slow queries in there. While I have not examined for "slowness" or to optimize them it would mean customizing Moodle code as this is default stuff.
So what can I do/try? I have reviewed the message boards and saw that a person or other has referenced how slow the quiz module is. As a matter of fact Moodle's performance page comments on it when it talks about how to get a true test of concurrent users.