Back in 2010, Gowalla launched a PubSubHubbub hub powered by Superfeedr that allowed for realtime notifications of checkins either by user or spot. Whereas before you’d have to subscribe to an RSS feed and check it every so often for updates, PubSubHubbub allows for you to subscribe to that feed and have them push the data to you as soon as an update is available. It’s very similar to the difference between checking mail on your iPhone manually or having it pushed to you automatically.
At the time, I was working on some funky Gowalla item stuff and so I wanted to use realtime notifications so that I could track items around the world. The biggest issue was that I’d need to manually subscribe to each feed which was tricky as there were around 3 million to follow at the time (it would have taken a month for all the subscriptions to go through if I looped through them one at a time and that doesn’t include the work to follow new spots as they’re created). I had been chatting to Julien Genestoux (CEO and Founder of Superfeedr) about getting access to the Track API which gets around that problem by letting you subscribe to feeds in a much more powerful way (e.g. by keyword, location, or hub). With access to Track, I’d be able to subscribe to every notification, in realtime, that Gowalla pushed out.
It was whilst chatting to Julien after SXSW that I realised that PubSubHubbub could solve my problems. By using the Track API, my server would be hit with data every time somebody checked in anywhere in the world with Gowalla. I could save that information each time and basically build up my own version of Gowalla’s database that I could search with a custom ranking engine. With the theory solved, it was time to get practical and put everything to the test.