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The following page will summarize some of the future work discussion for WDB.
We must ensure that WDB scales vertically with the hardware; i.e., increasing capacity by upgrading hardware specifications, while maintaining the physical footprint and number of servers in the server farm. Scaling hardware vertically simplifies site management, but at a higher hardware cost than scaling horizontally or improving software architecture. In addition, once you reach maximum capacity on existing hardware, you must begin to scale horizontally.
A key limitation in this respect is Postgres; version 8.3 however is vastly improved in terms of scalability compared to earlier versions of the database.