initial response time is too slow

Ok then, what were the internal server error?
Also, is the file you placed outside CI was the same as the one inside CI?
A controller with just an echo to test the performance should return in miliseconds, it’s really not normal to have a timeout.
Check your log files to see if there’s some error messages, because with the info you gave so far, there’s no way to know what is happening.

Yes both files are same file.
And its throws timeout or 500 error when load testing and there is no logs/errors captured by CI.
And when i test 1 api at a time through postman only the initial request takes time subsequent request works fine(CI startup issue??)
Is there any memory restrictions set by CI? as i can see that even when load testing with 5000 requests my server ram/cpu usage is very low