This is the backend scraper script to monitor submissions with specific words or phrases. To see mentions the moment they're made. Tracker search all of Reddit by default.
It scraps every post from Reddit in real time. Reddit gets about 500,000 new posts and 4,000,000 new comments every day. Combined, that's about 50/second. The posts don't come in at a contant rate, though, so we'd better be able to handle a few hundred a second.
Reddit offers a nice JSON API. We'll just use that to grab the most recent posts. It's at https://www.reddit.com/r/all/new/.json, and I recommend you open that up in your browser to follow along.