That depends on:
– how many posts you set to display
– how many plugins you use that act on the posts you set to display
If you set a sensible number, you should be fine.
Why did you pick 10,000 ?
Can i post more than 10.000 active posts and the speed of generating them will be the same as when there are only 100 posts?
In theory, it will be slower, but that’s just because how databases work. It’s not fault of WordPress’s.
When WordPress asks the database for all rows from the posts table matching the query, it still has to look through the whole database to find the matching rows.
In practice though, it shouldn’t be noticably slower as long as your server is decent.
If you’re really doing such a big site, consider using PostgreSQL for database. I think there was someone who made a PG version of WP sometime.
Postgres is nothing but a fork of mysql, there’s very little preformance difference between the two, and you’ll never notice unless you’re clocking down to the 0.001 seconds. mySQL has been proven to scale fine.
Actually, you’re wrong. PostgreSQL is much older than MySQL. Read up on it at http://en.wikipedia.org/wiki/PostgreSQL
There are also areas of performance diffrence, but that really depends on what you use it for and consequently what you test for.
