I have a REST API web server, built in .NetCore, that has data heavy APIs.
This is hosted on AWS EC2, I have noticed that the average response time for certain APIs are ~4 seconds and if I turn up the AWS-EC2 specs, the response time goes down to a few milliseconds. I guess this is expected, what I don't understand is that even when I load test the APIs on a lower end CPU, the server never crosses 50% utilization of memory/CPU. So what is the correct technical explanation that makes the APIs perform faster if the lower end CPU never reaches a 100% utilization of memory/CPU?