Jason Southwell addresses the problem of getting your database-driven web applications to scale seamlessly, showing how to implement database connection pooling to avoid those awful 'site busy...' messages.
Building professional web applications to guarantee successful deployment requires tedious attention to detail. This is a frustrating situation for anyone, but especially to those just starting down that road. Of course, preparing yourself by learning about common problems will make web development a much more rewarding experience. One of these problems is scalability, and it's one best solved at the design phase, whilst keeping it in mind throughout the development phase.
Here is a general scalability rule: the shorter the response time for each web action, the further your application will scale. The scalability of your application can be exponentially affected (adversely) for each additional second it takes to respond to a request. This article will give you a few hints on how to keep that response time to a minimum.
for the full article.