The Essential Performance Testing Metrics Every Developer Should Know

1.  Processor Usage: Time spent by the processor to execute non-idle threads.
2. Memory use: The available physical memory to process on a system.
3. Disk time: It is the time taken by the disk to read or write a request.
4. Bandwidth: Bits per second used by a network interface.
5. Private bytes: A specific number of bytes allocated to a particular process.
6. Response time: The time between the user’s request and the first response character.
7. Throughput: Rate of requests received per second by a network. (The formula is Throughput = (number of requests) / (total time). )
8. Maximum active sessions: Maximum number of sessions that may stay active at once.
9. Thread (user) counts: Determining the well-being of the application by checking the number of running and active threads.
10. Latency - JMeter measures the latency from just before sending the request to just after the first response has been received.
11. Think Time - the time between two transactions of user actions. 
    (Login -> Think Time -> Search -> Think Time -> Logout). 
    The average thinking time could be in the range of 3 to 10 seconds for a normal user.
12. Error rate - Measures the number of errors that occur in each request.
13. Network latency - Measures the time it takes for a request to travel from the client to the server.
14. Transaction time: Measures the time it takes for a transaction to complete.
15. Resource utilization: Measures the number of resources used by the server to handle requests.
16. Memory usage: Measures the amount of memory used by the server to process requests.
17. Load test scalability: Measures how well the server can handle an increasing amount of requests.
18. Page load time: Measures the time it takes for a web page to load.