Hypothetical: So, you have 26 companies using Basecamp (Company A-Company Z). Your single database server can't handle all 26 companies so you decide to shard

Hypothetical: So, you have 26 companies using Basecamp (Company A-Company Z). Your single database server can't handle all 26 companies so you decide to shard them. Your previous setup: Webhead1-|- Database1 Webhead2/ So, you have two webheads reading from one database. You need to shard and have a second database: Webhead1--Database1 (Companies A-M) Webhead2--Database2 (Companies N-Z) Easy! Think of it this way: because a person at Company A is never accessing Company Z's data, there doesn't need to be any communication between the databases. So, it shards in the same way that Wordpress shards: different sites are on different servers. With Basecamp, you don't need every company to be on the same server because you don't move data between companies. But you don't need a separate server for every company either. So, you can put a bunch of companies on the same server and a bunch on another server and you're done. There's nothing magic or RoR specific.