I’m experimenting with Redis-based caching for WordPress. Odds are that this page was actually served via a Redis page cache. If it wasn’t, it will be on the next visit. In the meantime, the Redis-based object cache plugin I’m also working on helped to generate this page.
The full-page cache plugin is very experimental, but you can find it on GitHub if you’re curious: https://github.com/ethitter/Redis-Page-Cache.