No caching

It’s almost the same as the built in search in terms of database requirements. MySQL uses indexing and caching as well for repetitive requests. The PRO version has application level caching featured, but in most cases MySQL cache is more than enough.
I’ve tested on 10 000 posts on shared 3 shared hosts (bluehost, hostgtator, 5host) and got results under 2 seconds with almost no peak mysql process usage.