Designed to offer enterprise - level functionality, the software can be deployed in a private cloud, directly on private servers, or on a public cloud. (inc.com)
However, the online version is running on a small private server hosted by the developer, which can occasionally have some issues. (android.gadgethacks.com)
More servers are obviously needed as soon as possible though you can play solo or on your own private server if you'd like. (articles.gamerheadquarters.com)