Performance is one of the non-functional requirements of an application. It defines the acceptable maximum response time for activities such as page load. It can also include the acceptable performance criteria for other activities which are application specific.
Performance requirements should be handled upfront while developing an application rather than optimizing application after the user starts complaining about slowness.
While designing an application the following two things should be considered to meet the acceptable performance criteria:
The maximum time taken by a query to fetch database records during peak load
The maximum time taken to execute a transaction […]