When FUSE first indexes your website or external content source, there will be a performance hit since we’re indexing potentially thousands of content items potentially going back several years. Performance is usually moot since it's a onetime event never to be seen again (unless for some reason a complete re-indexing is required again down the road). After the initial indexing, FUSE only indexes new items with no discernable performance penalty since it’s essentially the same as a web user requesting a webpage. We figure out what’s new content by performing a single item query at the next scheduled pull: Get most recent item from this content source. Does it match the latest item we already have in our index? If yes, stop. If no, get ten latest items. Now do we have them all? Rinse and repeat.
As for your website, there is no performance concern since we store your index in AWS and all of the computing power to run queries is happening there. A good analogy is YouTube. You can embed five hour long YouTube videos on a page on your site with no performance issues since the streaming/computing power comes from YouTube’s infrastructure.