2.3.5 Performance testing is critical

Important: Start performance testing as early as possible. The later you do performance testing the more expensive performance defects become.

In many projects testing is left for the end of the project and performance testing is usually last. As such, any delay in project execution impacts performance testing significantly. Any problems (such as performance issues) that happen during runtime usually have a much serious impact than any roadblocks you may encounter prior to going live. Also, many times performance issues are not trivial to address, so you do not want to discover them at runtime. So, it is imperative to plan for performance testing and tuning of your system sooner in your project, as well as allocating sufficient time to it.
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