%CPU reaching to 70% for 100 concurrent requests

When we try to run ab -n 1000 -c 100 http:// 127.0.0.1:3000/ %cpu almost reaching to 70%. Is this default nature of node or do we need to modify any settings of anything to decrease cpu usage?

Response of the request is just a "Hello world" and our machine is having 2GB RAM and node is running with current version.

I heard that nodejs can handle more than 100K concurrent requests but I don't understand how they achieve that.