Hi @ncbernar, sorry for the slow reply ;(
Looking at teh problem statement I would expect that this is just the “normal” case where you hit a performance limit (of some kind).
For an analogy let’s think of your server is a post office and people are coming to get packages.
Everything will work okay and as more people are coming more packages will be given to people. But at some point the max speed with which the worker in the post office can check that package is there, get it, check documents and let someone go will be hit.
At that point adding more people that want to get packages will just mean that they will wait longer as the worker can’t actually do this faster.
Looking at the http_req_duration it seemed like I was right at the start and then, not so much but I noticed that you are using a logarithmics scaling which is likely what is tripping both of us.
Given the rest of the info - transfering 70mb will utilise your network connection. To download it in 1s you need 70mb*8 = 560 mbps or moer than 1/2 of 1gbps connection.
Looking at the graph you seem to be at 16s at the end where you are having 30 VUs which kind of gives you exactly 1gbps of a connection.
So with that in mind it seems to me like this test will 100% be limitted by the network speed you can have between the load generator and the system under test. And the final performance of the system under test will also be limited by that.
You seem to be hitting the same problem as Influxdb reported a large number of errors when run k6 but in a small enough capacity that you likely don’t need to worrry.
Hope this helps you!