Identifying horizontal candidates

Before we can really decide how to spread our data across several database servers, we need to find appropriate candidates. To do this, we should start at the database level for databases that are extremely active. What qualifies as extremely active? Databases that fit any of the following criteria are a good start:

• The database experiences more than 10 million transactions per day
• The database handles more than 100 million queries per day
• The database writes more than 100 million tuples per day

Once we've chosen a database for horizontal scalability, we need to look at its tables and decide which should be distributed. Tables that make good choices are those that fit one or more of the following criteria:

• Tables that contain more than 10 million rows
• Tables that experience more than 1 million writes per day
• Tables that are larger than...