Now, eMusic isn't the world's biggest site, but it's nothing to sneeze at either. It serves around 6 million visits per month and "billions of HTTP requests" and millions of page views. The site has 400,000 subscribers. If it can handle eMusic, odds are it can handle your site as well.
But it won't do it straight out of the box. Taylor, lead PHP developer at eMusic, has been managing eMusic's transition to WordPress as a CMS platform away from Adobe's Day CRX. While he's a big fan of WordPress, he acknowledges that there's "a process" that you need to follow to get WordPress to scale. And "there will be blood" in the process. Expecting a seamless, smooth transition with no bumps? Not realistic.
Note that not everything is going to WordPress. Taylor says business logic and billing will still "live" in other services, while content, eMusic's UI, and community will all be served by WordPress.
In his talk, Taylor talks about planning the migration. This includes some basics like making a site map and inventory of content, as well as coming up with a "modular" import process and allowing for "turbulence." He also notes that you should expect to extend WordPress via plugins, and some you can use off the shelf. For example, Taylor says that the company is using Batcache for (well, duh) caching, bbPress for message boards, BuddyPress for social features, and Akismet for site spam. Well, to avoid site spam.
Taylor also notes that eMusic is making heavy use of Amazon Web Services (AWS), including EC2, S3, RDS and Elastic Load Balancing. eMusic's streams and downloads come straight from AWS.
The bottom line, though? WordPress does scale, says Taylor. If you have some time, kick back and watch the video of Taylor's talk. It's worth the 30 minutes or so, and will definitely give you some good ideas and tips on scaling WordPress. If you're working with WordPress on a larger site, or thinking about it, let us know what you're running into with WordPress.
Update: A number of commenters have decided to use this post to vent their frustrations with eMusic overall. Please don't. If you have comments related to this story, please feel free to leave them. If you have complaints with eMusic, please get in touch with eMusic. Further comments attacking Scott Taylor personally will be summarily deleted, as they're well out of line.