To find new podcasts, we use three approaches. First, we run crawlers 24/7 to find publicly accessible podcasts on the Internet, which is similar to how Google or other search engines find new websites. Second, podcasters submit new shows to Listen Notes on their own -- we get more than 100 new submissions from podcasters every day. Third, if we see any missing podcasts, we manually add them to our database.
We check the RSS feed of all podcasts 24/7. For recently-listened podcasts (based on our website and API traffic), new episodes would be added to our database within 1 hour (typically within 15 to 30 minutes). For other podcasts, new episodes would be fetched within a few hours - typically 2 to 4 hours.