Denormalize to Scale

Hank Williams recommends that Twitter denormalize its database so that it can be split up:

In typical normalized databases you would want to store every message sent only once and not in two places as I suggest above. But while perfectly normalized databases make for “cleaner” databases, they cannot scale. Database purists often speak of the merits of normalization. And certainly some normalization is generally necessary. But in the new database world, a perfectly normalized database is an un-scalable database.

Update: Twittering About Architecture.