Need the reason

[babu sh]

Most of the Servers speed is good whenever there are number of users & speed is slow whenever there are a few users.
what is the reason?

[Joe Ess]

It is impossible to give you a good answer without knowing the intimate details of your deployment environment.
My employer has an application that exhibits this kind of behavior. The developers blame it on load balancing, that until a certain load threshold is reached, the resource pools (caching, database pool, etc) are not fully initialized so performance suffers. Which begs the question, why don't they set an idle threshold rather than let all those resources expire only to reinitialize them for the next user.

[Joseph Antoine Raja]

babu

The answer is simple

when the less no of process and users are in server the CPU load/utilization will be low so your server process will utilize the maximum resources and events will be faster.

in case of too much of request and process the server has to wait for commit the events which will result in slowness.