If you know that there is an event coming up that will increase traffic to your website, it is best to begin testing as early as possible. By “event”, I mean things like marketing campaigns, an appearance on a national television show, or the approach of certain holidays.
While it often takes very little time to determine that you have a problem, remediating that problem can often take months. Also, be aware that fixing a bottleneck will always expose another bottleneck that was hiding beneath the one that you fixed. Often, you will need to a number of tests in order to isolate and fix enough issues that performance and scalability are significantly improved.
Examples of Issues with Quick Fixes:
A missing or out-of-date database index
Portions of an application that would benefit from implementing a caching scheme
A configuration issue is limiting bandwidth
Examples of Issues with Time-Consuming Fixes:
Large sections of application code need to be refactored