Page List RSS Feeds: Are they cached or generated on demand?

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We're using concrete5.7 to run a local news site. We have category pages w/ page list blocks that generate an RSS feed for each category, and articles are entered with Composer as subpages. Working great (mostly)....

I'm now in the process of developing an iOS app that presents our articles. Currently the app allows users to select a category, and it then loads the appropriate RSS feed from /feeds. Selecting a story launches a WebView of the article URL. However, the topic list is a bit sluggish, and I'm concerned about the load on our web server once it launches.

I'm wondering if each request to /feeds causes concrete5.7 to freshly generate the RSS feed files or if it generates them once and caches them like it does with pages and blocks? I've searched and can't seem to find a clear answer. If it's generating every time, I might investigate creating a job to recreate those files in a directory every X hours, then have the iOS app pull those cached versions. I'll also look into having the iOS app download all feeds at launch rather than on-demand when a category is selected, but I want to tackle the concrete5 side of it first.

Long term: I also want to figure out generating push notifications to the app based on the "Is Featured?" attribute and increase the number of articles in a feed from 20. What kind of performance hit are we looking at if I increase that value to 30 or greater? Any tips on push?

Thanks!