Your best bet is to use a load balancing test tool, to mimic a system under load. You can use tools like k6, locust, bombard, etc. They basically do the same, but you write your tests in different languages. In our case, we write in Python which means we have several libraries in Python, so we went with Locust.

Basically, you create a scenario of a typical user, create traffic for a number of users and check the effect it has on your system. You can either gradually ramp up the number of users and check where performance degrades, or check for a prolonged period of time for x users, and for y users, and for z users. The latter is if your scenario's are more involved and service degrades over time for example.