Best of this Week Summary 26 November - 2 December 2007

• Nice article on designing to facilitate unittesting, e.g. using interfaces to decouple an implementation class from its dependency.
  


• Here's a couple of reasons when to use and when not to use stored procedures. Most of the time it is not such a good idea to use them, except for example when having data-intensive/abstract computations, or batch-oriented operations.
  


• Interesting post on how PayPal is transacting 1500 USD per second(!) every day, and that their system is completely build in-house, running on thousands single-rack Unity servers. By using this kind of chunks (instead of a mainframe approach) they can upgrade a lot cheaper, because the servers are so cheap. This distributed, highly redundant Linux approach make the system a lot less vunerable to failures. A big benefit they have using open source is that it is a lot cheaper to have a development environment that is exactly the same as the production environment, therefore reducing the chance of inconsistent results and bugs caused by difference in environments.