Okay I found the trick, buried in the benchmark setup of s5cmd. The claimed numbers are _not_ reached with S3, but rather from a custom server emulating the S3

Okay I found the trick, buried in the benchmark setup of s5cmd. The claimed numbers are _not_ reached with S3, but rather from a custom server emulating the S3 API, hosted on the client machine. I think this is very misleading, since these benchmark numbers are not reachable in any real life scenario. It also shows that there is very little point in using s5cmd compared to other tools, since beyond 1.6GB/s the throttling will be from S3, not from the client, so any tool able to saturate 1.6GB/s will be enough.