Load Injector Payload is the number of virtual users simulated per Load Injector Server (LI Server). Payload affects the number of LIs the test requires and influences CPU utilization of each LI. 

You can set a custom Payload or apply the calibrated value while configuring a Stress Test.

It is important that Payload will not be set too high or too low. If it’s set to high LIs will hit its CPU limit and not be able to emulate all the virtual users. If Payload is set too low, LIs are not going to be used fully while more LIs than you actually need will be used for the test. 

Based on our experience, by default, we use the average Payload that is optimal to ensure ideal CPU utilization per LI (up to 80%) and efficient virtual user distribution between LIs. Although for maximum effectiveness it is recommended to apply Payload calibrated to your test settings. 

To calibrate your Stress Test device, on the Test Scenario page click Calibrate in the Load Injector Payload section.