The new rotation is designed to handle a large number of pages.
Here's a typical scenario: you have 300 categories, 7 pages per category, 3 sort options (ctr, date, duration) = 6300 possible pages. Add pages with embedded videos, and databases of 200,000 are not uncommon.
Creating this many pages via cron as static content would be inefficient, so pages are generated dynamically and cached. You set the cache time in the config. The shorter the cache time, the more pages per second the script must generate. This directly affects server load.
There's also the concept of “warming up” the site. For example, you've just finished setting everything up and are about to send traffic. If you send a large amount of traffic all at once—say 5k visitors—they'll spread across all pages and the script will need to quickly generate all of them, since the site is new and has no cached pages yet. To avoid excessive server load when launching a new site, it's important to ramp up gradually. Start with 1-2k per hour, which allows cache to build for the main pages. Then you can send as much traffic as you need.
Server traffic capacity: Once the cache is built, pages are delivered almost instantly. Here's how it works: when the first visitor hits the index of a new site, the script generates the index page and caches it for the duration you've configured. All subsequent visitors get this page from cache with minimal server impact. Even if 1M users access this page during the cache period, they'll get it without problems.
For a single site, whether you receive 50k or 500k requests, it doesn't matter much because you'll need to generate roughly the same number of pages either way.
However, if you have 50 sites with 10k each, the load is much higher than 1 site with 500k total, because you need to generate 50 times more pages (assuming the same database size and number of categories).
Database size also directly affects load: a 100k database translates to roughly 3000 pages depending on design, while 200k means 6000 pages.
To give you perspective: the maximum configuration we've seen is 31 sites on one server with 1.5M galleries total (roughly 5M gallery-category combinations and thumbnails), delivering 280 Mbps at peak.