1,000,000 listings of what? Optimum tuning to do what exactly?
Sorry, your questions are a little vague. These don’t seem to be WordPress-related issues, but rather configuration/optimization questions?
jobs listings
manage and listing them
probably not
Yes should I post these elsewhere?
If you want to get into the nitty gritty of PHP and MySQL optimization, you could try this section of the forum: https://wordpress.org/support/forum/wp-advanced. However you may want to look at places where PHP and MySQL are the main focus.
Tried that
It does not allow me to Post there for some reason!
Have also looked and not found much on MySql Tuning on WordPress.
I would have thought this was a fundamental
Which is disappointing – hence why I tried misc.