Maximum number of HTPP req/seq on EC2 instances

Do we have any benchmark on what is the maximum number of req/sec that we can achieve with gating on amazon EC2 instances?

I have currently tried on C5.Xlarge machine and I have only got around 400 HTTP request/second which is very low; I could do 5000 req/sec with vert.x on a same machine.

Am I missing any config? what should I expect from gatling how can I improve my throughput?