Yelp, the local search and review site, recently held an open house where Tech Lead John Billings demonstrates how that company uses Elasticsearch at scale in their environment. The video is accompanied with another presentation, but the portion that covers the slide deck starts at around the 16-minute mark.
Billings describes how Yelp constructs their Review search. All of this review data is stored in MySQL and pushed through an internal process to their Elasticsearch index.
This is well worth 11 minutes. The slide deck is on Slideshare here, but they are visible in the video.