Paper on redefining database optimization

Rethinking Cost and Performance of Database Systems [PDF] by Daniela Florescu and Donald Kossmann proposes a redefinition of the database optimization problem:

Traditionally, database systems were optimized in the following way: “Given a set of machines, try to minimize the response time of each request.” This paper argues that today, users would like a database system to optimize the opposite question: “Given a response time goal for each request, try to minimize the number of machines (i.e., cost in $).” Furthermore, this paper gives an example that demonstrates that the new optimization problem may result in a totally different system architecture.

The discussion and thoughts are particularly relevant for web applications that need to scale to large numbers of concurrent users.