• It is  a type of non-functional testing.
• Performance testing is testing that is performed, to determine how fast some aspect of a system performs under a particular workload.
• It can serve different purposes like it can demonstrate that the system meets performance criteria.
• It can compare two systems to find which performs better. Or it can measure what part of the system or workload causes the system to perform badly.
• This process can involve quantitative tests done in a lab, such as measuring the response time or the number of MIPS (millions of instructions per second) at which a system functions.
• Why to do performance testing:

• Improve user experience on sites and web apps
• Increase revenue generated from websites
• Gather metrics useful for tuning the system
• Identify bottlenecks such as database configuration
• Determine if a new release is ready for production
• Provide reporting to business stakeholders regarding performance against expectations

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