Designed for Use, 2nd Edition

Measure Speed

Performance matters. If your product involves a lot of waiting, people will not like the experience. You can and should test your product’s performance while it is still in development, using test data. But you just know that your users are going to do crazy things with your product—things you never even thought about.

If you’re writing a DVD cataloging application that allows people to keep track of the movies they own, you might assume that most people would own no more than 200 DVDs, so you might make sure that your product performs well for collections around that size. In reality, a sizeable portion of your customers are movie collectors (this being their reason for buying your product in the first place). So instead of keeping ...