I’m working with k6 to create stress test for an API. It’s working and i think i understand how it mainly works but i have something that i’m still not understanding.

So, i want to ramp up VUs like this :

scenarios: {
    ramping: {
      executor: 'ramping-vus',
      startVUs: 0,
      stages: [
        { duration: '10s', target: 10 },
        { duration: '20s', target: 10 },
        { duration: '10s', target: 20 },
        { duration: '20s', target: 20 },
        { duration: '10s', target: 30 },
        { duration: '20s', target: 30 },
        { duration: '10s', target: 40 },
        { duration: '20s', target: 40 },
        { duration: '10s', target: 50 },
        { duration: '20s', target: 50 },
        { duration: '30s', target: 0 }
      ]
    }
  },

And here is the result :

cloud result

As you can see, my users are ramping up over the time and the response time is also increasing. So my first question is : Why is the request rate still at the same rate when i’m increasing VUs ? In docs, i only found this : https://k6.io/docs/using-k6/scenarios/executors/ramping-vus/ It says that no matter of VUs, it will send as much http requests as it can. Am i right ?

If it is, here is my second question : Why is it better to do this for a stress test instead of increasing req/s with VUs increasing ?

Thanks for your responses